"I've just pissed in my pants. And there's nothing you can do about it!"
Anytime Cisco outsmarts any of the human characters, typically when he's being stolen from Dunbar and ends up escaping of his own accord.
When Dunbar rides up to the mourning Stands With a Fist on his mission to introduce himself to the Sioux, he gets her attention by noisily clearing his throat. She goes quiet and turns around...and then the frantically flapping American flag Dunbar is carrying with him blows around right into his face. Not exactly the best first impression. Doubly funny considering that Stands With a Fist will eventually become Dunbar's wife.
"I'm John Dunbar". "Dumb...bear."
When pretty much everyone in the Sioux camp knows about Dances with Wolves and Stand's with a Fist except Kicking Bird. He doesn't know until his wife tells him and he seems a little miffed that he didn't notice.
The smile she gets from the girl next to her when Kicking Bird ends her mourning sells it.
When Wind in His Hair and Smiles a Lot telling Dances with Wolves about the Sioux bride price, they are clearly both enjoying screwing with him. Wind in His Hair is even corpsing.