Continuity mistake: When Silent Bob renders the demon disabled by using the anti-odour spray, you see him take the spray out of his coat and spray with his thumb. However, it cuts to a front view, and he is clearly seen using his index finger. It then cuts to Bob's rear, and he is, again, spraying with his thumb.
Trivia: Kevin Smith has a love of Spielberg movies and makes reference to them in a number of his movies. In the scene where Silent Bob throws the pair off the train he remarks to a bewildered onlooker 'no ticket'. This is actually the same as in Indiana Jones and the Last Crusade, where Harrison Ford throws the German guard off the zeppelin and remarks the same line to a bewildered looking couple.
Trivia: When Jay drags Bethany behind the PA equipment and says that she'd agree to sleep with him if it was the end of the world, he pulls out a condom. If it's the end of the world, and existence is going to be undone, why bother with a condom? [It's a gag, rather than a mistake in the film. Worth keeping as trivia though.]
Liz: He said that faith is like a glass of water. When you're young, the glass is small, and it's easy to fill up. But the older you get, the bigger the glass gets, and the same amount of liquid doesn't fill it anymore. Periodically, the glass has to be refilled.
Bethany: You're suggesting I need to get filled?
Liz: In more ways than one. You need to get laid, Bethany Sloane. You need a man, if only for ten minutes.
Bethany: It's been my experience that the average male is never a man. Not even for ten minutes in his entire lifespan.
Liz: That'a a bit militant. You thinking of joining the other side?
Bethany: Couldn't do it. Women are insane.
Liz: Then YOU need to go back to church and ask God for a third option.
Bethany: I think that God is dead.
Liz: The sign of a true Catholic.