The Monkey Funeral
Yes. You read that right: monkey funeral.
Allow Shmoop to explain.
When Joe first pulls into Norma's driveway, trying to escape the repo men, Norma thinks that he's the undertaker for her pet monkey's funeral. Because that's what you do when you have a monkey that dies.
And when she discovers Joe isn't in fact an undertaker for apes, she orders him out of the house. But he ends up staying when he convinces her to let him help her with her screenplay. Later on, at night, he witnesses the monkey funeral through the window:
JOE: There was something else going on below: the last rites for that hairy old chimp, performed with the utmost seriousness—as if she were laying to rest an only child. Was her life really as empty as that?
Joe thinks that Norma's life is empty because she's forced to seek companionship from an ape. Um, duh? She doesn't want a real human relationship, but a dancing monkey to obey and amuse her. This foreshadows what will happen to Joe himself: Norma probably doesn't really love him, but she needs him to love her or at least give her simulated affection and pay attention to her.
After sleeping at Norma's house for the first time, Joe has a dream that seems to foreshadow his own fate, in which he says he saw a chimp dancing for pennies (of course, a chimp isn't technically the same as a monkey, but we'll let that slide). Since he'll become Norma's gigolo in exchange for gifts and money, we can assume that it has more than a little future, personal relevance:
JOE: That night I'd had a mixed-up dream. In it was an organ grinder. I couldn't see his face, but the organ was all draped in black, and a chimp was dancing for pennies. When I opened my eyes, the music was still there… Where was I?
Where are you, Joe? Dude. You're the chimp.