Picture of Yip Yip Costume
Whether you loved them as a kid or hated them for giving you nightmares, there's no denying it's fun to go around freely and anonymously shouting "yipyipyipyip" to those around you. Here's how to make a costume based off the Martian Yip Yip aliens from Sesame Street.

UPDATE: Some pics from WonderCon 09!

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Step 1: Materials

Picture of Materials
5-6 yds of Curly Fleece
I've found this fabric to work well for the body of the costume. It's soft, breathable, and light enough to move around in but with enough weight to hold the package together. The downside to curly fleece is it can shed quite a bit when it's fresh, so it gets rather messy. However, a good thing about this is that the fur on the fabric was so long that it easily hid the many safety pins I used. Another good option is something called Flurr (fleece + fur). You want about about 2.5-3x whatever your height is.

1-1.5 yds of Black Chiffon/Mesh
This is the mesh-like material that will form the mouth. It is important that the material be see-through, since this will be your window to the outside world. The mouth will probably consist of 2-6 layers of this material, depending on the specific fabric you have. The most important part is that if you hold it up to your face, you can see relatively clearly through to the other side (usually there is a light source outside of your costume), but no one can see into your costume through the mouth (no light source within your costume).

Contour Shaped Sponge
You can pick this up at your local Home Depot for a few dollars. A good half-oval shape is what you want. The dimensions I found were 7.5"x3.5"x2.5", and I eventually cut in half length-wise however. This will form the lip.

Styrofoam Spheres (x2)
For the eyeballs. 4" in diameter will do, or 5" if you want to go bigger.

This will be essential to keeping the costume on your head. Pick out something that is light, nothing too thick. You don't want to start sweating too much while wearing the costume. It should have enough structure to it though stay firm and not flop around.

Pipe Cleaners
This should match the color of your costume. Thin pipe cleaners work well, you just need to buy enough of them to twist around to make a solid and flexible pair of antenna. Some glittery pipe-cleaner is also helpful in complimenting the solid colors.

Other materials:
Hot glue gun
Needle and thread (or staples)
Safety pins (various sizes)
A friend (very helpful to have someone to wear the costume as it is being created)

Step 2: Measuring the mouth, part 1

Picture of Measuring the mouth, part 1
Drape the body fabric over your head length-wise so it runs from your heels, over your head, and down to your toes. However, give yourself approx 1 1/2-2' of extra length for the front half. This is because you'll need the slack for when you lift up what will be the jaw portion of the costume to move the mouth. Duct tape is a handy measuring marker for this step. While draped in the fabric, mark these points on the fabric:

Center of the top of your head
Eyebrow line (approx upper edge of mouth)
1 3/4' from the brow line to the lower edge (of the mouth)

These will be markers for cutting out the mouth hole. The dimensions of the mouth hole are approximately 1' in width, and 1 3/4' in length, oval shaped. Mark the left and right edges of the mouth hole as well. Your eyebrow line will be the the approximate upper edge of the mouth. Be sure these markers all line up symmetrically with the length-wise axis of the fabric.

Next, cut out the mouth hole. Better to under-estimate here, you can always increase the size of the hole with more cutting. Keep in mind that whatever you imagine the hole size to be, leave a small 1" buffer between the edge of your cut, and the true edge of the mouth. This is because you'll need that flap to sow on the mouth covering.

Post Note: I recommend making the upper area of the mouth slightly more square than rounded. This is so that you will have enough room to have a bit of peripheral vision when you look through. If you don't manage this, you can widen the width of the hole by fastening the fabric to your beanie accordingly.

Step 3: Measuring the mouth, part 2

Picture of Measuring the mouth, part 2
Next cut out a rectangular piece from the black mesh to act as the mouth fabric. Be sure it has plenty of space to cover the hole. Depending on the transparency of your fabric, you'll need several sheets to form the mouth. With my fabric, 3-4 layers was enough.

A good test of the visibility is to hold the total number of sheets close to your face and use a take a picture of yourself (with flash on) from several feet away. Your silhouette should not be visible, or only very slightly. At the same time, you should be able to see through the fabric and walk around a dimly lit room at least.

Step 4: Sewing the mouth

Picture of Sewing the mouth
Here comes the tough part. After you've decided how many layers you want to form the mouth, you're going to sew them to the body fabric to cover the hole. It helps to tape the black sheets together first so they can be sewn on all at once. This part can get frustrating as each layer may move about on it's own, but just take your time. The good thing is, complete accuracy isn't important, from the outside, no one can tell.

IMPORTANT: Be sure you're sewing the mouth fabric to the inside of the body, not the outside.

If you're not comfortable with a needle and thread, ask a friend who knows how to help you. Stapling is also an option, but that depends on the thickness of your mesh mouth fabric. After you've sewn the mouth fabric on to the body fabric, you can trim the loose flaps to clean up the area. From the outside it should look like a nice gaping black hole.

Note: A commenter suggested using hot glue for this step, which probably would make things alot easier. Other commenters have used velcro strips to make the mouth area detachable. This sounds like it would be especially helpful if you want to be able to show your face easily without taking off the whole costume.

Step 5: Fitting the beanie

Picture of Fitting the beanie
You've probably noticed by now that when draping the body over yourself, it tends to slide around a bit. To fix this, you'll need to attach your beanie to the inside, right where you've marked the center of the top of your head. You can use large safety pins to get a rough position, then lock it down in place with smaller ones around the rim. When adjusting the placement, be sure your eyes are just beneath the upper edge of the mouth fabric, so you can see out through the mouth. However, you don't want your eyes to be too low into the mouth, or it may look like either your Yip-Yip is always looking down, or it's upper lip is wrapping around your forehead.

Step 6: Creating the jaw

Picture of Creating the jaw
With the dimensions of the sponge I bought, I cut it in half length-wise to make it thinner (easier to handle). Mark an area a few inches past the lower edge of the mouth, and tape the curved face of the sponge onto the inside surface at that location. This is where all the movement will take place. Try moving the jaw up and down while looking in a mirror, to make sure it looks ok. When you're satisfied with the placement, hot-glue the sponge on.

Once the jaw is attached, you may notice the mouth fabric feeling a bit floaty. You can weigh it down to give a it a better sense of being a "mouth" by pinning a small weight to the inside of it to create a sort of "throat". A knot of left-over fabric works well for this.

One tip, when holding up the jaw in the "closed" state, your eyes should fit just between the tip of your jaw and the upper edge of the mouth. This way you can still see without your Yip Yip opening his mouth.

Step 7: Creating the eyes

Picture of Creating the eyes
While inside the costume, have someone else mark a good position for the eyes, just based on whatever looks best. Another option is to lay the costume out flat on the floor, then lay the eyes on the approximate area according to what appears symmetric. Once you have that, you can hot-glue the balls directly onto the fabric. I prefer to have the eyes touching each other, so I glue them together as well.

Test the eye position by placing the costume on with the beanie a comfortable and even place, then look if the eyes appear to be straight and level. When that is taken care of, cut out a pair of circles for the pupils out of black paper (mine were about 1" in diameter), and glue them onto the Styrofoam balls.

Step 8: Creating the antenna

Picture of Creating the antenna
Take the pipe cleaners and wind them up into a single shape as seen in the images. I used about 24 total pipe cleaners to get the structure right, with more making up the base and less around the ends. When it was all wired together I lined it with four glitter pipe cleaners, just because.

When you have the finished antenna, affix it to the head area with safety pins, just behind the eyes. The safety pins can go through the beanie for extra support. Adjust the antenna so it stands up straight when the costume is worn normally.

Step 9: Finishing touches

Picture of Finishing touches
While inside the costume, have someone start sealing up the sides with safety pins. Fold the flaps inward and close them up. The safety pins can be about 6-8" apart, going down the side. Just clean it up however you feel comfortable, as long as you can keep others from seeing into the costume from the sides. Don't close it up too tightly though, you need space to move around, and to maintain the Yip Yip look. It doesn't have to be super neat, the Yip-Yips have a pretty sloppy look. And in the end, you're still essentially just wearing a sheet over your head. (Commenters have opted to sew up the sides or use velcro strips, both which work fine. Safety pins are probably the fastest option. In any case, you may want to leave a hole for you to let your arms stick out in case you'll need them)

With the sides sealed up, you can get to work on the front and back edges. What I did here was cut vertical strips up length-wise like a flier with tear-away phone numbers. I also cut out strips from left-over fabric and attached it to the ends. The more the better, it will help to cover up your feet and legs. Not too long though, you don't want to trip over it. The idea is just to give the costume that ghosty-alien look. You can either hot-glue the extra strips on, or use safety pins, whichever you prefer.

That just about wraps it up. If you need to adjust how the costume fits, you should be pretty comfortable by now with how much flexibility you have; I used safety pins pretty liberally as they aren't easily seen anyways being fastened on the inside. When not wearing the costume it seems easiest to handle it with your hand inside the beanie like a puppet; this way none of the headgear flops around too much. Feel free to give me feedback, or share any ideas you've added to your costume.

yipyipyipyipyipyipyip...uh huhh, uh huhh
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gryphyn made it!5 years ago
Just wanted to share my version. I used adhesive velcro to hold the sides shut and a 10" Styrofoam wreath wrapped in duct tape for the mouth. After gluing have of the wreath for the mouth edge, you can hold the other half and flip it up and down. Sorry the pics are sideways. I can't sort out how to rotate it since they appear correctly oriented on my Mac.

jen.maitland made it!5 years ago
Hi there,
Thank you very much for these instructions! my sister have made 2 yip yip costumes for this halloween (2009).
a few things we did different were....
1. we sewed up the sides of the costume....we found that this was harder to get into but it became more sturdy....we left a 8" gap so our arms can come out but it folds over so you can't see the gap.
2. we couldn't find a foam peace so we purchased some 1" styrofoam and made it into tombstone shape and placed a stick in the middle, wrapped it in duct tape and attached it to the mouth.....still allowed it to be flowing and allowed for a handle as well.
3. we wraped gardening wire around the pipe cleaners so that we could get more structure in the cleaners themselves.....
Here is how one of our costumes turned out!
kqrpnb made it!5 years ago
Here's my Yip Yip.  Made it in just a few hours.  Here's how I modified the instructions for my budget:

1. I bought regular Fleece instead of curly fleece.  It's cheaper, plus we found it on sale.

2. We put up 4 layers of black chiffon for the face, but so far we've cut on layer off from the inside cause it's a bit too dark.  We expect maybe one more layer will come off by Hallowe'en

3. For fit, I started the fabric in the back just about touching the floor.  Then up over the head, grab the 'mouth' where it's comfortable and fold your arms to under your eyes. Trim the front to the same level as the back (you may want to wait until you are done constructing the mouth though)

4.  I sewed up the sides instead of pinning.  After you finish the mouth and get the cap on right (we safety-pinned a baseball cap turned backwards), make sure that the fabric is at the same level at front and back with your lower jaw in place just below YOUR eyes (not the yip yip's - you want the jaw where you can see over it to walk).  Once that's trimmed level, just flip the costume inside out, hold the corners of the front and back together and sew a half-inch seem all the way up to about 20" from the fold.  Don't over-complicate this: Imagine folding a bedsheet in half, then sewing a half inch seem from the open end to the closed end, ans stopping 20" before getting to the closed end.  This leaves room to poke your arms out, but is loose enough to hide your shoulders if you tuck it in.

5. Antennae: take two pipe cleaners and hook them together end to end to make a long one.  Make 5 or 6 of these, then twist them together in pairs, then again, until all are twisted together as one sextuple-thick, double-length pipe cleaner.  Take 2 more and wrap them around one end to form the pom-pom.  This makes ONE antenna.  Do it all again for the other.  What I did then was to put these two together and wrap another pipe cleaner around the end to bind them together.  This will make a V-shape out of the antennae.  Now make a small L on the bound-together side.  This gets glued to the fabric, and the rest of the bound portion gets glued to the back of the eye-balls where they meet.  this gives a lot of stability to the works, plus it let's you curve the antennae around the eyeballs like the real yip yips.

6. Mouth modifications:  Now that the costume is all sewn up, but before you glue the eyes and antennae on, I made one practical change.  Find the inside bottom point of the mouth when it is in position under your eyes.  Sew through the chiffon a 3"-4" diameter circle centered around that bottom point.  Then cut an X through the chiffon circle, and safety-pin a pillow case to the inside of the costume so that it catches whatever candy is thrown into your mouth!
Rachyl is a Yip Yip.jpg
Emaleen kqrpnb5 years ago
 Does adding the pillowcase have to be done before adding the eyes and antennae? 
kqrpnb Emaleen5 years ago
 Thanks Sliny!

@Emaleen: I would do every single thing you can before attaching the eyes and antennae.  You should make sure everything works as you want it, then glue the eyes and antennae, otherwise you stress the hot glue when you turn it inside out or take it on and off.  You know?
sliny (author)  kqrpnb5 years ago
great job, especially on the pillow case. :)
Peekadosies made it!5 years ago
heres my yip yip costume
nice instructables
KualoJo made it!5 years ago
yip yip!
redstarsrbija made it!5 years ago
GREAT INSTRUCTABLE! I made one of these suckers and wore it to my college all day on Halloween lmao such great reactions! I even mastered the yip yip speech lol I used a tennis racket for the mouth, made it ALOT easier lol the chick on the right seemed to like my costume so she wanted a picture
sliny (author)  redstarsrbija5 years ago
Nice idea with the tennis racket. You do lose one thing though, with the soft squishy sponge, lots of people come by and giggle when they squeeze your "lip". :D
Yould you please make an instructable on it please
lol i used this one right here. what difference would it make if i made one?
I commented earlier and I asked for a yip yip hat.You see?
Spifferoo made it!6 years ago
Thank-you for this great idea! We also won best costume. A four year old just loved us and asked if we were in costumes ... he was so convinced we were martians!
NCBob made it!6 years ago
Awesome instructable. A friend and I at work made them and entered our costume contest and we won best group costume :) Only thing we did different is we used a sewing machine to sew the mouth, it was much faster and turned out great. EXCELLENT instructable!!!
NCBob NCBob6 years ago
(removed by author or community request)
sliny (author)  NCBob6 years ago
Awesome! Congrats on the award!
NCBob sliny6 years ago
Ok, got the full video of the skit and uploaded it. Even though they introduce us as the Yip Yaps :)
noelrossiter made it!6 years ago
Thanks - a wonderful set of instructions. Here's my creation used at a 40th birthday party (TV themed) last weekend in Hobart Australia
sliny (author)  noelrossiter6 years ago
Awesome work, I'm sure you had alot of fun with that!

Oh my god, I love the aliens! Do you remember the one that goes,
"Ra-di-o!"? You did a fabulous job, and thank goodness the kids went
for it! It's uncanny how much it looks like the yip yips. :)

pingh made it!4 months ago

This was such a great idea. Based on the items in the comments, we used velcro as well to hold our mesh in place. We used a single layer of black chiffon for the mesh which was easy enough to see through while nobody could see in.

Great times indeed.

MelissaB35 months ago

where could I buy this in winnipeg

MelissaB35 months ago

where would i buy this in winnipeg

CelineVerena made it!11 months ago

Thanks a
lot for these awesome and useful instructables. We also won the Best costume

A few
things we did differently:

We stuck the layers of black mesh together using hot glue instead of tape
& we did not sew the mouth to the fabric, but we used velcro strips, which
we stapled to both the fabric and the black mesh.

2. We
attached the eye balls to the fabric using hot glue and pins which we stuck
from the inside of the costume through the beanie and the fabric into the
Styrofoam eye balls. This worked out well.

3. We
attached the eye balls to each other using double-sided tape and a toothpick, because
the hot glue made the Styrofoam melt. Double-sided tape and a toothpick weren’t
enough to hold the eye balls together the whole evening, but we had some extra
double-sided tape with us;)

4. We attached
the antennae to the eye balls using pins. This didn’t work out too well,
because the pins kept coming loose.

5. We didn’t
seal up the sides with safety pins, but wrapped the back part of the costume
around our waist and attached it with a safety pin on the front side. A lot
easier and works well too;)

ttttiff1 year ago
on the previous step i noted the fragile state of our eyes, so what ended up working for us here was to hot glue (on low temp setting) the eyes to the antenna. we created a little semi-circle, c-shaped, base with the end of the pipe cleaner, and set the eye on top, secured with the glue. then we trailed the antenna up the back and secured the antenna with sewing pins criss crossed into the eyes. liquid nails would also work better for this. we hot glued (high setting) the base portion we created with the pipe cleaner to the top of the head and put some extra glue around the bottom to kind of "seal" it. then we just shaped the antenna out. they held all night.
ttttiff1 year ago
we had quite a time trying to attach our eyes. the hot glue was just melting the styrofoam. we tried tape and super glue also, with no success. on one, (due to damage between the eyes caused by the hot glue) we ended up using liquid nails, which kept them pretty damn solid all throughout the night. on the other costume, there wasn't as much damage, so i used a tooth pick to connect them (half the tooth pick in each eye) in the center and just put a little of the liquid nails in between, just in case.
mothman01 year ago
Can you clarify where you suggest pinning the weight to weigh down the mouth?

Is it attached to the approximate center of the black fabric?
dwelch11 year ago
Can't wait to make these....
I LOVE this costume idea! My boyfriend wants to make this to celebrate 'carneval' in the Netherlands, can't wait untill february!
Mostmom1 made it!2 years ago
Thanks again for a great instructable! We had SO much fun with these!!
IMG_3006 - Version 2.jpgIMG_3007.JPG
Mostmom12 years ago
I made these for my daughter and her best friend this year. People loved them!! We used half a styrofoam ring on the inside for the mouth, regular fleece, and those gigantic pipe cleaners for the antennae. We bought 6 yards for each costume and had a lot left over. We used two layers of chiffon for the mouth and they ripped one off, after it got dark, so they could see. This was a toasty warm/dry costume too, which was good, since it was a cold, wet Halloween.
It's a costume, it's a muppet, it's awesome. :)
mausmobile2 years ago
My husband and I just got home from a Halloween costume contest. I still can't believe it - we took first place!

People loved the costume, but I think they loved the act more. We walked around the bar several times, looking things up in our book, yipping at people, and letting them take pictures with us. There were some pretty elaborate costumes, but ours had the most character.

Thanks so much for your awesome instructable. You helped us turn our idea into reality!
jfaulstich3 years ago
Here's my attempt at the Yip Yips. My neighbor and I worked on these in one night. It took about 4.5 - 5 hours.

It was also insanely expensive. Not many places sell the curly fleece anymore, and the one place we could find (JoAnn Fabrics), only had it in one bright color, red. The rest of the colors were off-white, white, brown, and spotted, so they weren't exactly traditional Muppet colors. We purchased the red curly fleece (at $75 for 6 yards) and then opted for a cheaper, yet similar material in pink ($45 for 6 yards). I would strongly recommend using a cheaper material like Crushed Panne Velvet. It comes in a variety of colors and is more breathable. The only downside is that it doesn't hide pins, glue, etc. as well as the curly fleece.

In the end, the effort and money spent were pretty well worth it. People were beyond giddy at the reference (if they got it...we got a lot of "Elmo!" and "Hey Cookie Monster!" too) and were amazed we made them ourselves. My only regret was not enrolling ourselves in a costume contest or 2. Given the cost of the costumes though, I plan on using this for many a costume party and Halloween for years to come. Thanks for this Instructable!
blatour23 years ago
Me and my friend Anjali made these for halloween! We are both 12 and we know the yip yips because my dad used to watch them when he was little! :) I would upload a pic but I don't have one on THIS computer, hopefully somtime I will be able to uplad it! Thank instructables!! (:

vdillon13 years ago
Where do you guys find the curly fleece at? I can't seem to locate any.
sliny (author)  vdillon13 years ago
I found it at JoAnns fabric stores. I would think that the larger retailers would have them, or at least something similar in quality.
cazeliea3 years ago
Help! I am really eager to make this costume, but the only two fabric stores around me only carry this fabric in red, black, brown, white, and gray... ! I'm making one for myself and someone else, so I don't want to have two red yip yips (and those other colors are definitely not yip-y enough).

Does anyone remember the name of stores they found their curly fleece from? I'd love to email those stores or call them and see if they have any. Once I saw the curly fleece in real life, I really, really don't want to use a stand-in fabric.. the curly fleece is so good!

Thanks for any help!
sliny (author)  cazeliea3 years ago
I found it at JoAnns fabric stores. I would think that the larger retailers would have them, or at least something similar in quality.
solemnraven3 years ago
That's so awesome.
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