The original pattern for this hat was made back when Adventure Time was a short featured on Nickelodeon, and then after it failed to do anything on that network, it made it's way to the internet. This hat is much more like the original "pilot" hat, where it's less of a tube with a face hole. This one has straps that you can tie underneath your chin.

The design for this hat came from my good friend Nate Little. However, he has been caught up in graduate school, and has had seemingly no time to write an Instructable. After months of kindly hinting and nudging him to write one about his hat design, and him never doing so, I simply asked if I could. Obviously, he said yes, and even helped me out. He even let me use his camera while I'm away at college. If you have the time, or like supporting your resident Mad Artisan, check out these links.

Mad Artisan Labs - Facebook
Mad Artisan Labs - Etsy

Step 1: The Pattern + Materials

The pattern is attached in PDFs below. When printing them, be sure to not "shrink to fit" or anything like that. The images are sized to 8.5 x11, and need to print in that size or else your pattern will be too small.

Some assembly is required with the pattern. The "Main Flap" piece is divided up into 5 or 6 different pieces and they need to be taped together, but I've made it so there are letters to help you align the pieces.

Once you get the pattern assembled, and ready to go you're going to need to gather some materials.

1 Yard of Fleece (White or off-White)
Appropriate colored thread
Scissors
Pins
Sewing machine (optional)
Sewing needle (for the ears, or the whole thing)
Fabric scissors

Note: Fionna Variation
The only difference between Finn's hat and Fionna's hat is the length of the ears. If you want to make her hat, simply make the ears longer. I didn't include this in the pattern.

Note: Sizing Issues
There have been a few users who have found the final product to be much too large. So if you find yourself having a particularly small head, or perhaps this will be made for a child. It's a good idea to print the pattern at a reduced size. Testing the printed pattern by assembling it and wrapping it around your head is always a good way to make sure it the final product will fit.

Note: Seam Allowance
The seam allowance is very forgiving throughout this project, and mine ranged anywhere from 1/4" - 1/2"

Step 2: Cut It Out

You can lay out your pattern, so that you have the least amount of waste, by placing the "Hat Top" in between the "Main Flap." Since you need to cut two of both of these, it's a good idea to fold your fleece in half while you cut.

Here's how many of each part you need.

Ear (x4)
Main Flap (x2)
Hat Top (x2)

Step 3: Sew the Ears

Let's start off easy by sewing the ears. Pin each pair of ear fabric together, and sew around the top edge. Make sure to leave the bottom open.

Step 4: Sew Main Flap + Hat Tops

Find both of the "Main Flap" pieces that you cut out. We're going to be sewing up the back edge of each one. Fold a piece in half, then pin the back edge. Try to sew the edge as close as possible, or else you'll have weird lumpy seams sticking into the back of your head when it's all finished. Do the same for the other "Main Flap."

Next we need to pin each "Hat Top" to each "Main Flap." Try to do it evenly, or you may end up with some pleats in your hat (which we don't want). Take your time, and when you think it's good sew the pieces together.

You can give the hat somewhat of a test fit right now. Keep in mind that it's "inside out" and we still need to flip it in a later step.

Step 5: Attach Ears

The ears in this picture are a little larger than the one included in the pattern. To make sure the holes you cut are the right size, flip the ears, so they're "right-side out." This is the way we'll be sewing them in. Cut your holes (only on one part of the hat, leave the other alone for now), keeping in mind that there is the seam from the "Main Flap" to act as a marker to the back of the hat.

Once the holes are cut, pin the ears in place. Remember to flip them "right-side out" before pinning them in their respective holes. Now that they're in place use a back stitch (by hand) to secure them.

Flip the whole piece "right-side out" when your done.

Step 6: Final Assembly

You should only have two pieces of the hat left now.

Main piece with ears (flipped "right-side out")
Main piece without ears (flipped "inside out")

Take the piece without ears and place it on the table. Next, take the piece with ears, and put it inside the part you just put on the table. Be sure to line up the back seams. Once you have everything lined up, pin it along the unconnected edge. You'll be sewing it almost completely together, except you need to leave a 2-3 inch gap anywhere on the piece to flip it right side out. I chose the leave a section by the back seam open.

We're almost done!

Step 7: The Flip + Finishing Stitch

Now you need to pull then entire hat through that little hole you left. When you finally get everything through the hole it should look like some kind of weird fleece turkey. Simply push half the hat without ears into the side that has ears, and it's almost done!

You need to seal up the remaining hole with a ladder stitch.

Step 8: Bonus Step! - the Backpack

I was originally planning to do a separate Instructable for the backpack, but decided it was pretty easy to make, and it would be hard for me to accommodate the different sizes of people, and the different functionalities. The one I made in this step is fairly functionless. I still have the option of adding a zipper on top, but don't have one at school (where I made it). Other people might want it to function like it does in the show, as the light green part being a flap that has one large black button.

Either way, if you're interested in making one, you can skip through the pictures, and read some newly added steps(below) and probably get a decent idea of how I did it, and base yours off of that.

1. Cut out the pieces.

(x2) 14" circle (one of each color)
(x4) 22" x 4" strip (2 of each color)

2. Cut some more...

Cut each circle in half.
Cut one light green, and one dark green in half, so you will have (x4) 11" x 4" strips, and (x2) 22" x 4 " strips.

3. Start sewing.

Fold the smaller 11" strips in half (the long way) and sew along the edge. These will be parts of the straps.
Pin each of the long 22" strips to the corresponding colored round edge of the half circle, and sew along that edge.

4. Straps.

Flip the 11" strips, so they're "right-side out", and insert each light green tube into each dark green tube, and sew them into place, attaching them to each other.

5. Top piece.

Pin the straps onto the remaining half circle (I chose to start with the light green). Next, pin the other half of the light green top to the half circle with the straps you just pinned. Sew along the edge, finishing the top half of the pack.

6. Bottom piece.

Do the same for the bottom half. Pin the straps in (making sure they aren't twisted), and sew it up.

7. Finishing.

Now we need to sew across the middle of the pack, attaching the light and dark green parts. It's been inside out the whole time, so you need to leave about a 2 inch hole so you can flip the whole pack.

Hopefully those simply written steps and pictures can get you through it.

Step 9: All Done!

Now that you've got the hat, all you need to complete your Finn costume are some blue shorts, blue shirt, green backpack, and a magical yellow dog.

I get comments emailed to me, so if you have any questions, feel free to ask away!

One last thanks to Nate Little at Mad Artisan Labs. Be sure to check out his Etsy store, and become a fan on Facebook.