Made out of foam padding, lots of glue, some paint, and slime.
I found a great way to make slime while making this costume. Its super easy and super cheap. Here is how:
Elmers Clear Gel Glue
Concentrated Icing Coloring
Liquid Detergent(Tide, etc.)
It is pretty much mix the ingredients until you get it right for what you are using it for, but I found that about half a bottle of the glue, a little dab of blue and yellow coloring (to make green), and about a teaspoon of detergent does this trick for a good slime.