It's both. "Heel" is used once, a a throwaway joke (and was also the reason that the writers used the name). "Sit" was used twice: once when Phoebus arrives in Paris, and again during the final battle.
Your Mileage May Vary, but several moments involving the gargoyles are quite funny, including most of "A Guy Like You" (Hugo cross-dresses as Esmeralda and the gargoyles say Quasi is shaped "like a crossaint is", when they mishear a conversation and come to the conclusion that "Frollo's nose is long and he wears a truss" and when they all appear to be sketching Esmeralda, except Hugo who sketches Djali the goat instead. And the last moment of the film, where the orchestra pauses for a frustrated Laverne to yell at the birds, "don't you ever migrate?!".
And let us not forget this epic exchange after Phoebus and Quasimodo decide to go find the Court of Miracles:
Phoebus: Truce? (He pats Quasi on the back encouragingly)
Quasimodo: Well...okay. (He hits Phoebus in the spot where the arrow hit him, causing him to groan in pain) Sorry.
Phoebus:: ...no, you're not.
A lot of Quasimodo and Phoebus' interactions during this period of the movie is hilarious.
And then there's Clopin, indulging in a bit of literal Gallows Humor:
Clopin: Any last words?
*Quasimodo and Phoebus, being Bound and Gagged, can only make some indecipherable noises*
Clopin: (rolling his eyes at the Fourth Wall) That's what they all say.
Immediately followed by:
Clopin: Now that we've heard all the evidence— [interrupting himself with a hand puppet] Wait, I object! [as himself] Overruled! [as puppet] I object! [as himself] Quiet! [as puppet] ...Dang.
"I'm free! I'm free! ...Oof! ...Dang it."
The entire Esmeralda/Phoebus scene in the cathedral, but especially:
Phoebus: You fight almost as well as a man.
Esmeralda: Funny, I was going to say the same thing about you!
Phoebus: That's hitting a little below the belt, isn't it?
Laverne's ongoing conflict with the pigeons, culminating in "DON'T YOU EVER MIGRATE?!!!"
The part when it emerges that Frollo taught Quasimodo his alphabet using words like abomination, blasphemy, contrition, damnation, eternal damnation, and forgiveness. It's both a blessing and a shame that they stopped at f; one wonders what the rest of the alphabet would have been like...
Absolutely everything in Esmeralda's chase/escape sequence; the best parts would have to be the aforementioned "I'm free!" bit, and Phoebus, after ducking a ricocheting helmet, in dazed admiration: "What a woman!"
The gargoyles building a fully functional catapult from assorted items found in the cathedral and then... shoving it off the roof onto the soldiers.
Victor: "Are you sure that's how it works?"
Made even funnier when the catapult crushes a few soldiers in a manner similar to a mouse trap.
Hugo: Works for me!
"The city of Paris is glowing tonight. Sure, that's because it's on fire, but still there's l'amour."
