Hook up a Makey Makey to right arrow key input. Wire the right input to a tin foil strip and the earth input to another tin foil strip. If you place a conductive object between the two strips of foil, the squirrel should tell you "Yes, the object is conductive." If the object is not conductive, squirrel will do nothing.
Thanks to Colleen Graves for this project. I changed it up a bit for my class.