1. Any printer paper or card stock will work. I like the card stock because it is more sturdy but we didn't have any around so the kids grabbed printer paper.
2. Decide what you want to make. Using any size envelope cut out the shape for the mouth to open and close. Then create your animal around the mouth, cut, color, paste whatever you like.
My son's dracula
My daughters mouse and 3D cheese she pasted.