"Sorry, I have to lie to make my magic work. It's in my contract." :|
"What? That's ridiculous."
A contract is shown. "See? I had to sign over some of my truthfulness for magical power. Really, signing over stuff like this is common. There's a reason there's so many wizards who don't wear pants."
"Wait, you mean that wizards give up...wearing...pants?" Incredulity. (and a psyduck-like pose)
"Sure. I mean, it's nothing major. I just gave up something different."
"Because I like my pants." :3
Context is musing on the origin of the word "warlock."