Definitions by bbf
Lobster
A prank to play on an unsuspecting female friend. You approach her silently from behind, and with both hands reach around and tweak her nipples, and yell "Lobster!" She will probably freak out and scream -- this is the desired effect.
Scorpion
A prank to play on an unsuspecting male friend. When they least expect it, you silently approach them from behind, and thrust your entire arm through their legs and reach up towards their face, thus cradling their junk with your bicep. At the same time, you must yell "Scorpion!", and watch as they freak out.