I remember I was watching Good Eats with Alton Brown a few years ago and he had a special about gelatin. Here is his recipe, it looked really realistic. Give it a try. Here's a link to his recipe.
Brain:
http://community.buycostumes.com/forums/AddPost.aspx?ReplyToPostID=31790&Quote=False
Heart:
http://www.foodnetwork.com/recipes/alton-brown/cinnamon-cherry-heart-recipe/index.html
I ran my mouth out off a bit too much, oh what did I say? You just laugh it off, it was all okay. And we'll all float on okay...
Float On - Modest Mouse