Egon: "There's something very important I forgot to tell you."
Venkman: "What?"
Egon: "Don't cross the streams."
Venkman: "Why?"
Egon: "It would be bad."
Venkman: "I'm fuzzy on the whole good-bad thing. Whattya mean "bad?"
Egon: "Try to imagine all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light."
Ray: "Total protonic reversal...."
Venkman: "Right, that's bad...OK.. important safety tip. Thanks, Egon."