You need silly putty. You just gotta put a small wad of silly putty on the underside of a door nob, and wait for your victim. (You should put the silly putty there in a way that you can't see it until you are touching it!) The silly putty has to be pink, like bubble gum. They will touch it, and think it's gum!
Damien: Double ugh (touching something unknown and squishy, then "gum"), only to find out it's not really gum ^_^. Nice touch, Kendra.