For my school's sports carnivals I like to dress up, and as green house captain this year, I had to do a good job. I made a Yoshi costume for the swimming carnival, and I think it worked pretty well.

By the way, I recommend NOT doing it during the hot Aussie summer like I did ;)

Step 1: What You Need

This is the equipment that I would recommend.

Head:
   • 2 beach balls (somewhere between 40-70cm diameter, depending on head size)
   • Glad wrap (cling wrap, saran wrap, whatever you call it in your country)
   • Newspaper
   • Flour
   • Water
   • PVA glue
   • Cardboard
   • Green paint, white paint and red paint or red tape
   • Black permanent marker
   • Strong tape
   • Clothes pegs/clamps
   • Scissors/knives

Tail:
   • Cardboard
   • Masking tape
   • More paint
   • Elastic
   • Stapler
   • Glad wrap

Body:
   • Green shirt (preferably long sleeved)
   • Green gloves
   • Long green pants
   • White material/shirts
   • Large brown shoes, I used a pair of ugg boots
   • Backpack and a brown covering for the shell

Step 2: Plan

Start off by planning.
Take some photos of yourself, draw some pictures, figure out the scale of everything.
I mostly worked off a Hungry Jacks Yoshi figurine which was approximately 20 times smaller than real life. This will help you determine the size of the beach balls.

Step 3: Paper Mache Mini-instructable

This instructable requires a fair bit of paper maché, so here's how I made it. Feel free to use your own recipe.

1. Half-fill a plastic chinese take-away container with warm water.
2. Pour in some PVA glue (the more the better, I only used a small amount).
3. Here I added some plaster of paris. After a while I realised that the plaster does more harm than good. Don't use too much.
4. Flour. Lots of flour. Not too much, but enough to get a fairly thick mixture.
5. Dip a strip of newspaper in the mixture (I found that newspaper tends to rip one way much neater than the other)
6. Use two fingers to squeeze off excess mixture back into the container
7. Apply the strip

Step 4: Paper Mache the Beach Balls

First, I paper machéd the beach balls. I planned on being cheap and saving a couple of dollars by reusing the beach ball. This was nearly a very bad idea but it turned out ok. If you want the main head and the nose to be nice and smooth, make sure you get two balls.

Cover the ball with a layer of glad wrap in case the paper maché sticks to the ball. Apply the strips to the ball, do as many layers as you need to until it is fairly hard. I think I had ~6 layers on each ball.

Once dry, cut around the circumference if it is for the nose. (If you are only using one ball, the first should be the nose) You will probably cut the ball. Having the two eggshell halves makes the inside dry better and will make later steps easier.

For the second ball, it is important to know that the head is more elongated than the nose. If you are reusing the first ball, it will probably deflate as you cover it. When you cut the head, just cut a hole in the bottom (where your head will eventually go). If you had reused the ball, it will probably have sunk on the point it was standing anyway. Mine did, so rather than cutting a hole, I just never made that section.

Step 5: Paper Mache the Eyes

For the eyes I blew up two balloons to a small size and tied a string around them to get the desired shape. In the end, my eyes were a bit too small.

Step 6: Make the Spines

To make the spines, cut some pieces of cardboard the right size. I used three pieces for each of the three spines. Two on the edge and a spacer int he middle. wrap some tape around these. Optionally paper maché.

Step 7: Attach the Nose and Head

To attach the nose and head, I cut 16 or so wedges radiating from the centre of one half of the nose, and the side of the head. Then I put them together matching (roughly) triangle to triangle and folding them alternately into each half. It actually helped that my triangles weren't even, since this provided more friction and I could wear it without any tape. Peg/clamp the wedgesdown and tape them with very sticky tape. Chances are the tape won't stick to the paper maché but give it a shot.

Step 8: Attach the Eyes, Spines and the Rest of the Nose

Cut the sides and bottoms of the eyes so that they fit together and tape them. Cut holes out of the front to see through. My original plan was to have some mirrors in a cardboard box as an old-school periscope to see out of the eyes, but in the end I just dipped the head down and was able to look through, after I cut a hole in the top of the head/nose connection.

Line up the front half of the nose with the back half and tape them together.
Tape the spines on.

Add another layer or two of paper maché over the whole thing.

Step 9: Paint!

It may be a good idea to first draw in the lines with the permanent marker, but, beware that the white paint can sometimes let the ink come through as a bright blue line, it even showed through after a couple of layers.

Paint the nose and half of the eyes and head green. Paint the rest white and paint the spines red, or wrap them in red electrical tape (I did).

Be careful what paint you choose. My newspaper was still readable after 3 layers of the first green paint, so I had to get a different one. It may be a good idea to do a white base layer.

Also, try adding some PVA glue to the paint to give it some extra shine.

I went around each of the edges with permanent marker once it was all dry.

Step 10: The Body

I used a green t-shirt and trackpants (that was all I had and they matched) for the base of the body. For the white belly, I found a white shirt (which had a NES controller on the front) and turned it inside out and folded the sides in. I simply taped it to the green shirt and used a couple of safety pins. I also put some stuffing in that I got from some cushions the the school was throwing out. I planned to have the top and legs stuffed, but it ended up being too difficult.
For the white part of the pants I used a white bag, but I probably put too much stuffing in there.

Step 11: Tail + Backpack

For the tail I got two large pieces of cardboard and cut half a line (is that possible) down the middle of each to put them together, then wrap it in masking tape to paint the top half. Then I wrapped it in glad wrap for extra protection. This was the night before I needed it so I was pretty rushed, there are probably much better ways to achieve it.
In the morning I stapled loops of elastic around where the legs and waist would go. The waist one kept snapping so I eventually just tied knots.

For the saddle I just covered my backpack with the orange cover of one of the cushions I borrowed and held it with staples and safety pins.

Step 12: Wear It!

I put some sponges in the head area for support and clipped some spiky bits. Then I put it together and wore it in the hot sun the whole day, it wasn't as bad as I thought. I won best dressed (as per usual), which was good. I've restored the clothes to their normal condition. The nose-head connection is becoming very weak and I fear the paper maché is attracting mould, but for the moment, its just a decoration.