For extra credit, Annie is putting on a Dia de los Muertos (like Spanish Halloween, but not the sexual position) for Spanish class. She wants her party to impress Troy so she begs Jeff to come. However, Jeff just acquired permission from Britta to ask out his hot statistics teacher, Professor Slater (who rejected him anyway), but he eventually agrees to go. Jeff shows up at the party, but takes off with Senor Chang to go to the faculty party to try his moves on Professor Slater. Just as things are looking decent for him and he claims she doesn't have to worry about him telling his friends, he has none, suddenly the entire breakfast club shows up needing his help. He sends them away, but it's too late, the damage is done. Jeff uses a line given to him about Senor Chang where he basically begs for sex and it works! He begins walking home with her.
Meanwhile, at the Dia de los Muertos party, Pierce is busy trying to feel young and cool again. He wears a Beast Master costume and ends up exchanging some of his actual medicinal pills for some of Star Burns' entertainment ones. He ends up having a bad trip and tries to hide under a fort he made of desks. The rest of the gang goes looking for Jeff and finds him outside walking home with Professor Slater. Proving he's an amazing friend, he passed on his guaranteed booty to go inside to talk Pierce into coming out of the fort before it collapses and kills him. As he talks Pierce out of it, Pierce gets excited and knocks the fort down, nearly killing them, until Batman (Abed dressed up) swoops in and saves their lives.
Also, throughout the episode, Shirley (dressed as Harry Potter) helps Britta get revenge against Professor Slater for "stealing Britta's man." Britta doesn't actually want to get the revenge, and it's more so crazy Shirley acting out against her ex-husband. It turns out he shows up at her door asking for his old ring back he... he wants to give it to his new woman. She's upset he moved on and didn't come crawling back... for her to be able to reject him. Poor Shirley, we totally <3 her.