When Raj tries to eat with the guys in the cafeteria, his sneezing gets him banished by the germophobic Sheldon to another table. Sheldon has to talk to Leonard giving him the official 24-hour notice (according to the roommate agreement) that a non-related female will spend two days at their apartment. She is a human female, as no pets are allowed, other than seeing-eye dogs and cybernetically-engineered helper monkeys. She is Dr. Elizabeth Plimpton, the world-famous cosmological physicist from Princeton University. Sheldon and she have been corresponding for years about gravitational wave signatures of inflatons in the early universe. Leonard is a huge fan of hers. She will sleep in Sheldon's room though not sharing the room.
Walking up the stairs, Sheldon questions Penny on his choice of maxi-pads in his bag, whether the wing design is just a marketing ploy. Naturally, Penny needs it explained, and Sheldon tells her about everything he bought for his lady friend: scented soaps, pantyhose, Midol, calcium chewables, and the yogurt that is good for regulating the female bowels. Sheldon requests that Penny not waste her time with a lot of female banter, such as hair styles, shoe styles, mudpacks, or Brad Pitt and Angelina Jolie.
Dr. Plimpton shows up at the door. Sheldon insists Leonard play it cool, since years from now, Sheldon's biographer might ask him questions about this event. Dr. Plimpton remembered to write their building number on her left hand, because her right hand contained the coordinates of a new neutron star, and she didn't want to visit there since she would be crushed by hyper gravity. She says hello twice like Sheldon and Leonard did when they first greeted Penny. She appears to be a bit ditzy. Sheldon greets her, and Leonard is rather nervous to meet Dr. Plimpton, shaking her hand three times and saying "hi-lo." (A combination of hi and hello.) Sheldon apologizes because he is only an experimental physicist. Dr. Plimpton admits that some of her friends are experimental physicists, though not her best friends.
Sheldon shows her to his bedroom and gives her the tour, rules and regulations. Gloves are available to wear if she wants to peruse his comic book collection. She also has an emergency 8-day ration kit is at the ready in case of disaster. Dr. Plimpton does ask about the relationship status of Leonard. Sheldon explains his former relationship with Penny, which was over as inexplicably as it started. They wish each other good night or good luck in case they have an apocalypse.
Later, she decides to visit Leonard's room because she can't sleep. He's reading her book and is on Chapter 6. She tells him a little secret that she wrote it completely naked. A confused Leonard finds that it doesn't read that way. She shows him, recites some of it and drops her robe as she quotes from her book. The two go on to have sex.
Everybody wakes up in the morning with Sheldon doing morning vocal tests and Leonard and Elizabeth coming in together. They had more than a pleasant night while giggling together. She is having coffee when Penny stops by to request a ride to work because her car is out of gas. She is introduced first to Elizabeth. Elizabeth says she was really enjoying her stay and then looks over at Leonard and giggles. Penny picks up on her body language. Sheldon suggests that she use the bathroom because she doesn't want to follow Leonard. Leonard goes to get dressed, but Penny stops him telling him that they just broke up. She doesn't care if he wants to sleep with Sheldon's doctor buddy. Sheldon is offended that Penny would suggest it. Penny isn't suggesting it. She maintains that it already happened. Sheldon is shocked at what Leonard did, who claims that it wasn't his fault. Sheldon then feels that that implies that he accidentally tripped and fell into vagina|her lady parts. Penny is not happy about this turn of events and decides to take the bus, just in case Leonard slips on a banana peel and gets her pregnant. Sheldon is shocked by the betrayal of him and doesn't want Leonard playing with his friend.
At the cafeteria, Sheldon and Elizabeth stop by the table after Howard and Raj can't figure out Leonard's clues as to what he did the prior night. She wants a coffee, but not black. This time, she wants it hot, brown, and sweet while making eyes Raj.
Later Howard shows up at Raj's apartment for Halo Night and finds Elizabeth at his apartment. Elizabeth wants Howard to stay for some role playing games though not the Dungeons and Dragons type. She runs into the bedroom to get ready. Howard is shocked and tells Raj that he broke up with Bernadette weeks ago. Leonard shows up and Elizabeth is excited about that. He wants to know what is going on and Howard welcomes them to the Penthouse Forum. Elizabeth is down to her bra and Raj shoos everybody out to make a dramatic entrance. Then he locks Howard and Leonard out and has her to himself.
Later, walking up the The stairs, Penny asks about Dr. Slut Bunny. She doesn't think he needs to know, but Leonard has to explain why he did it. She let him.
- Guest starring:
- Teleplay: Steven Molaro, Jim Reynolds & Maria Ferrari
- Story: Chuck Lorre, Bill Prady & Lee Aronsohn
- "You can't argue with good farce. Even in a short scene like the one we got at the end here it can generate tremendous easy laughter. Dr. Plimpton tries to seduce Raj, Howard and Leonard at the same time leading to a really funny punch line...The problem was the writers couldn't decide who the story was really about. The first half of the episode was all about Sheldon as the writers exploited every amusing thing he could say about a female guest coming to stay. Then once Leonard slept with Dr Plimpton the episode became about him and how Penny would be affected by his dalliance...A fun episode with plenty to keep you chuckling. But wait for it...this could have been so much more." - The TV Critic's Review
- IMDb user reviews
- Title Reference: Dr. Elizabeth Plimpton comes to visit Sheldon for the purpose of a job interview, but winds up seducing the three other guys and having sex with Leonard and Raj.
- Chuck Lorre's vanity card 
- This episode was watched by 13.73 million people with a rating of 5.3 (adults 18-49).
- This episode aired in Canada on May 10, 2010 with 2.3 million viewers and a weekly ranking of #8.
- Episode transcript 
- Howard and Bernadette broke up in this episode.
|BDG Spectrum||Unknown (but it's BAD!)|
Seen in the bins in Sheldon's bedroom:
|Batman & Robin #5
|Batman & Robin #8
"Batman vs Batman"
|Batman & Robin #9|
Rise & Fall Special
- Howard mentions to Raj that he and Bernadette are broken up; it is later revealed the reason why they broke up in "The Hot Troll Deviation" (S4E4).
- Sheldon states, "pets are banned under The Roommate Agreement, with the exception of service animals, such as seeing-eye dogs and, one day, cybernetically-enhanced helper monkeys." In "The Zazzy Substitution", "The Luminous Fish Effect" and "The Ornithophobia Diffusion", Sheldon violates this rule.
- The yogurt is referred to again in Season 5, "The Weekend Vortex".
- Chapter six of Dr. Plimpton's book The Effervescent Universe covers the cosmic distance ladder#extragalactic|distance scale extragalactic distance ladder. Therein, she references the Wilson-Bappu effect, expounding, "When we consider the absolute magnitude brightness of varible star#pulsating variable stars|pulsating variable stars, we start to see a possible explanation for some of the discrepancies found in Hubble’s constant." [Drops night gown.]
- Sheldon seems to have no problem sleeping in the couch in this episode, even though previously he forced both Penny and Howard out of their beds onto the couch and floor when he slept over at their places.
- Sheldon makes another heed on his comments regarding Penny's "Check Engine" light.
- When Penny declines Leonard's offer to drive her to work, she says that she's worried he'll slip on a banana peel and get her pregnant. This is a nod to "The Creepy Candy Coating Corollary", when Bernadette mentioned that her mother wouldn't let her ride bikes in fear of hitting a bump and losing her virginity. Both instances involve some form of accident leading to a "sexual" slip up.
- Leonard, Raj, and Howard decline a foursome with Dr. Plimpton because they don't want to be naked in front of each other (again). In "The Electric Can Opener Fluctuation", they reveal that they slept together naked when the heat went out on their Arctic expedition. Both Howard and Raj did sleep together with the fat Sailor Moon cosplay girl from Comic-Con.
- Leonard has trouble saying hello to a new female as he did with both Penny and Alicia in Season 1 and Season 2, respectively.
- [The scene: Raj's apartment. Howard knocks at the door and Raj answers.]
- Raj: [irritated] What?
- Howard: What do you mean, "What?" It's Halo night.
- Raj: I can't. I'm too sick. [coughs] Go away!
- Howard: That's why we moved Halo night here. [holds up a paper bag] Look, I brought my mom's chicken soup.
- Raj: I'm not hungry.
- Elizabeth: [from inside the apartment] Don't send him away. Let him in.
- Howard: Who’s that?
- Raj: I bought a parrot.
- Howard: Yeah, right. [goes in and sees Elizabeth on the couch] Dr. Plimpton?
- Elizabeth: Hi. Howard, right?
- Howard: Uh, yeah.
- Elizabeth: Do you like role-playing games?
- Howard: Yeah, sure. In fact, I'm a Dungeons and Dragons|dungeon master.
- Elizabeth: Not tonight. Tonight, you are a delivery man. You brought soup, but, uh-oh! Raj and I don't have enough money to pay you. So we'll have to come to some other kind of arrangement.
- Howard: Beg your pardon?
- Elizabeth: You two figure out the details. I'm going to change into something I don't mind getting ripped off my milky flesh. [She goes into the bedroom and closes the door behind her.]
- Howard: What the frak?!
- Raj: Go away! She wants New Delhi, not kosher deli. Besides, you have a girlfriend.
- Howard: We broke up weeks ago.
- Raj: Why didn't you say anything?
- Howard: I was waiting for the right time. This is the right time.
- [Leonard arrives.]
- Leonard: Hey, who's ready for Halo?
- Raj: Oh, this is like a nightmare. Get lost!
- Howard: He's right. The numbers are shaky enough as it is.
- Leonard: I don't understand.
- Elizabeth: [opens the bedroom door slightly and peeks through] Oh, good. Leonard's here!
- Raj: Good?!
- Leonard: Elizabeth? What's going on?
- Elizabeth: What's going on is you and Howard are my moving men and Raj is my new landlord and I don't have enough money to pay any of you! [She goes back inside the bedroom and closes the door.]
- Leonard: Is she suggesting what I think she's suggesting?
- Howard: Yep! Welcome to the Penthouse Forum.
- Raj: Okay, show of hands. Who’s up for this? [Howard quickly raises his hand, but is the only one to do so.]
- Leonard: We’ll all be naked in front of each other.
- Howard: [quickly lowering his hand] I’m out.
- [Elizabeth emerges from the bedroom wearing a bra and a very short skirt.]
- Elizabeth: Everybody ready?
- Raj: [whispering to Howard and Leonard] Follow my lead! [to Elizabeth] Almost. We’re, we’re going to go out into the hallway and, uh, make a dramatic entrance.
- Elizabeth: Oh, good. It’s so much better when everyone commits! [She sits on the couch.]
- Raj: Run. Run, run, run. Don’t look back.
- [He hustles Howard and Leonard through the doorway. After they're out, he quickly closes and locks the door, then turns around and looks at Elizabeth.]
- Raj: So. You say you can’t pay your rent?
- [In Leonard's and Sheldon's building, Leonard happens on Penny in the lobby as she's on her way up from the laundry room.]
- Penny: Oh, Leonard?
- Leonard: Hey.
- Penny: I found these in the dryer. [holds up a pair of Spider-Man briefs] I’m assuming they belong to Sheldon.
- Leonard: Thanks. It’s really hard to find these in his size. [They start walking up the stairs.] So, listen. I’ve been meaning to talk to you about the other morning.
- Penny: You mean, you and Dr. Slutbunny?
- Leonard: Yeah, I wanted to explain.
- Penny: Well, you don’t owe me an explanation.
- Leonard: I don’t?
- Penny: No, you don’t.
- Leonard: So you’re not judging me?
- Penny: Oh, I’m judging you nine ways to Sunday, but you don’t owe me an explanation.
- Leonard: Nevertheless, I’d like to get one on the record so you can understand why I did what I did.
- Penny: I’m listening.
- Leonard: [after a long, long pause] She let me.
- Elizabeth: Ah, Dr. Cooper, thank goodness. I completely forgot your address. But then I remembered that I’d written it on my hand. Lucky for me, I didn’t confuse it with what I’d written on my other hand, which are the coordinates for a newly discovered neutron star. ‘Cause if I tried to go there, I’d be crushed by hyper-gravity. Anyway, hello.
- Penny: You know what? It’s, it’s none of my business. If you want to sleep with Sheldon’s doctor buddy right after we stopped seeing each other, go for it.
- Leonard: Well, now…
- Sheldon: Excuse me. I’m uncomfortable with you recommending that Leonard pursue having intercourse with Dr. Plimpton, who I assure you has better things to do.
- Penny: I’m not recommending it. I’m saying it already happened.
- Sheldon: That’s preposterous. Tell her, Leonard.
- Leonard: [hesitantly] Well…
- Sheldon: [aghast] No.
- Leonard: Come on. It wasn’t my fault.
- Sheldon: The implication being that you somehow tripped and fell into her lady parts?
- Penny: You know what? I’m just gonna take the bus to work.
- Leonard: Penny, I can still drive you.
- Penny: Oh, no, no, it’s okay. You might slip on a banana peel and get me pregnant.