In the season four finale, Raj becomes Sheldon's new roommate, which leads to a surprising encounter with Penny. Meanwhile, Howard has issues with Bernadette earning more than him, and Leonard gets a surprise regarding his relationship with Priya.
- Bedmate Reveal: As the episode ends, Penny wakes up to find Raj in bed with her.
- Crazy-Prepared: As he gives Raj a tour of the apartment, Sheldon reveals that he has indicated the path to the emergency exits with luminescent paint.
Raj: You're kidding.
Sheldon: [turns off lights to reveal glowing arrows on the floor] I never kid about safety.
- Hard on Soft Science: Amy, a neurobiologist, belittles Bernadette for studying microbiology.
Amy: I'll make it simple for you. I study the brain, the organ responsible for Beethoven's Fifth Symphony. Bernadette studies yeast, the organism responsible for Michelob Light.
- MD Envy: With Bernadette having earned her doctorate, Howard is now the only non-doctor in the group other than Penny. To rub it in, Penny notes it while serving them at the Cheesecake Factory.
Penny: So that means you're a doctor, you're a doctor, you're a doctor, you're a doctor, and Howard... you know a lot of doctors!
- That Came Out Wrong: Raj says it word for word in this exchange when Penny discovers that he's moved in with Sheldon.
What happened to Leonard? Sheldon:
Same thing that happened to Homo erectus
. He was replaced by a superior species. Raj:
I'm the new Homo
in town! [Beat
] That came out wrong.
- Wrongfully Attributed: Raj says he is paraphrasing Shakespeare when he says "It's better to have loved and lost than to stay home every night and download increasingly shameful pornography." The actual quote — "Tis better to have loved and lost than never to have loved at all" — is from Alfred, Lord Tennyson.