In their first adventure, Supes and Bats fight a legion of supervillains out for a 1 billion dollar bounty on Superman's head posted by Lex Luthor. Surrounded and vastly outnumbered, the duo stand back-to-back, and we get this gem:
Batman: I think we can take them. Do you think we can take them?
The 'K' arc (from which the chibi League debuted) had a number of other funny moments, and made even funnier because most of them involve the normally Comically Serious Batman, if not actually being delivered by him:
The ridiculously inaccurate Superman/Batman movie, which takes...a few liberties with Batman's character, making him a blond who had a sister, with both being victims of child abuse, and having him inspired to become Batman because of the baseball bat wielded by his father. His batcave is also on the moon. All the while the real Batman and Superman are watching the filming process; Bruce is not amused, but Clark sure is.
Batman: (internal monologue) This is ridiculous.
Superman: (internal monologue) This is hysterical.
And later in the same scene...
Superman: (internal monologue) I have strength enough to move mountains... I'm not sure I'm strong enough not to laugh right now.
After Superman is recovering from being hit by Kryptonite shrapnel, he wears an eyepatch to cover the damaged eye and approaches Batman and says he has a question for him.
Batman: (sporting a visible grin) No, Clark. You can't borrow my pirate ship.
Superman gets exposed to a new type of kryptonite and has the munchies.
While Superman is fighting a losing battle with "The American Boy," a Doomsday clone modified to have Kryptonitebone protrusions, Batman flies in on his Batwing to assist.
Batman: (sporting another visible grin) Damn, I really liked this one. Fastest top speed yet.
*Batman crashes the Batwing into "The American Boy."*