when you're walking down the hall and a boy comes up to you looking for a good time. and he goes "hey, what would you do if i just put my nuts on your forehead?" and you say "then i'd put MY nuts on YOUR forehead" is accepting invitation to go smoke some pot while listening to peters techno...
this only works if you're a girl.

When you're being horny (especially around friends) and as a result shame ensues.