This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Cats Don't Dance
Sawyer's backstory. She came to Hollywood with dreams of becoming a famous singer and dancer, and even though she was clearly talented, she never got any roles (since she's not human) and had to become a secretary for a talent agency.
Woolie: Ah, poor Sawyer. I thought she'd be the one to make it. Such a dancer, with a voice of an angel... Danny: I never would have guessed... Woolie: That's what this town does to you, my boy. It wears you down. Danny: But I thought Hollywood was always looking for new talent. Woolie: Talented people, not animals. You see, the spotlight will never be on fellows like you and me. And it's foolish to think otherwise, Danny.
Also, once you know her backstory, a lot of her dialogue is quite depressing to listen to, especially this exchange:
Woolly giving up all hope after Danny inadvertently helps Darla frame them for the studio's destruction. His dreams, along with that of all the others crushed, he tells a guilt-ridden Danny that he should go home.
The Bus Driver's Wham Line as Danny is on the bus heading back to Kokomo. But it's seeing Pudge that really seals it.
Bus Driver: Look at them out there, poor fools, they ain't got no future. Heh. What am I telling you for? You're not trying to be something you ain't. You're leaving this mess all this behind.