At the prom, Santana is singing "Love You Like a Love Song," originally performed by Selena Gomez and the Scene. While she sings, Mercedes and Sam are dancing and laughing. Mercedes sees her old man-mountain of a boyfriend dancing with a new girl, and they give each other friendly smiles and nods. So I guess she didn't ruin his life.
Also on the dance floor are Quinn and Finn. She's sitting in her chair, holding his hands, vaguely bobbing along to the music. While he just stands there. But it's not just his normal horrible dancing that's keeping him so stiff -- he's still furious with Quinn for lying about being able to walk. He starts yelling at her to stand up. New Guy With Gross Hair Whose Name Demian Can't Be Bothered To Look Up comes over to calm things down, and Finn accuses him of being in on the secret. There's a little bit of pushing before Sue breaks it up, asking Finn if she's really going to have to eject him from prom two years in a row. He decides to leave on his own. Commercials.
Anti-prom. It sucks, as everyone is well aware. Kurt suggests to Blaine that he'd be okay with it if Blaine wanted to go to the real prom. But Blaine won't give in to Brit-Brit's anti-gelism. He's worried that Kurt won't find him attractive with the giant hair that he'll have without gel. There's a knock at the door. It's Finn. He asks where Rachel is, just in time for her to emerge from the bathroom in her prom dress. He tells her, "I love you, you're beautiful, prom sucks without you." So they kiss and decide to go to the prom. Blaine decides that if Brit sees him, he'll just pretend to be an ice sculpture until she walks away. So he and Kurt are also going. But Becky and Puck decide to stick it out. After everyone else leaves, Becky locks the door and asks Puck if he's ready for some strip poker.
Cut to a slow-mo shot of Finn, Rachel, Kurt and Blaine entering the prom. Don't they know what will happen if prom and anti-prom collide? Streamers, everywhere. It's not pretty. Brit welcomes them as they enter. She's thrilled to see them, but reminds Blaine of the anti-gel rule. So Blaine leaves to ... wash his hair, I guess? I'm bald, so I don't really know from product. And then Artie, Sam, Demian, Mike Chang and New Guy With Gross Hair Whose Name Demian Can't Be Bothered To Look Up are singing One Direction's "What Makes You Beautiful." Oh, look, Will and Emma are dancing in the crowd.