[Shrek and Donkey are on their way to rescue Fiona. Donkey sniffs the air, and smells something horrible.]

Whew, Shrek, did you do that?! Man, you gotta warn somebody before you crack one like that. My mouth was open and everything.

Believe me, Donkey, if that was me, you'd be dead. [sniffs] It's brimstone... we must be getting close.

Yeah, right, brimstone, don't be talking about no brimstone. I know what I smelt and it wasn't no brimstone, and it didn't come off no stone neither.