Spengler: There’s something very important I forgot to tell you.
Venkman: What?
Spengler: Don’t cross the streams.
Venkman: Why?
Spengler: It would be bad.
Venkman: I’m fuzzy on the whole good/bad thing. What do you mean, “bad”?
Spengler: Try to imagine all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light.
[...]