Raj (Kunal Nayyar
) tries to eat with the guys in the cafeteria, but his sneezing gets him banished by Sheldon (Jim Parsons
) to another table. Sheldon has to talk to Leonard (Johnny Galecki
) anyway, handing him the official 24-hour notice (according to the roommate agreement) that a non-related female will spend two days at the apartment. A human female, as no pets are allowed, other than seeing-eye dogs and cybernetically-engineered helper monkeys. Dr. Elizabeth Plimpton (Judy Greer
), the world-famous cosmological physicist from Princeton. Sheldon and she have been corresponding for years about gravitational wave signatures of inflatrons in the early universe. Leonard is a huge fan of hers and is excited about Dr. Plimpton being there. She will sleep in Sheldon's room. Howard (Simon Helberg
) has a two-part question.
HOWARD: Are you kidding me? and Seriously, are you freakin' kidding me?!?!?
However, they wouldn't be sleeping in the same bed. He goes to prepare, and Leonard and Howard let Raj back at the table. And he proceeds to sneeze all over their food.
At the apartment, Sheldon questions Penny (Kaley Cuoco
) 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 bowel.
PENNY: You're having a woman stay with you?
SHELDON: Yes. Why does that seem to flabbergast everybody?
Sheldon requests that Penny not waste her time with a lot of female banter, such as hair styles, shoe styles, mudpacks, or Brad and Angelina.
Dr. Plimpton shows, and Sheldon insists Leonard play it cool, since years from now, Sheldon's biographer might ask him questions about this event. Fortunately, Dr. Plimpton remembered to write their address on her left hand, because her right hand contained the coordinates of a new neutron star, and she didn't want to visit there. 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: I apologize. He's only an experimental physicist.
DR. PLIMPTON: Not to worry. Some of my best friends are experimental physicists.
Sheldon shows her to his room and gives her the tour...and rules and regulations. The gloves are available to wear if she wants to peruse his comic book collection, and the emergency exits and emergency 8-day ration kit is at the ready. Dr. Plimpton does ask one question: what the relationship status of Leonard was. Sheldon explains his relationship with Penny, which was over as inexplicably as it started. She decides to visit Leonard's room because she can't sleep. He's reading her book and is on Chapter 6.
DR. PLIMPTON: Can I let you in on a little secret? I wrote the section on the Wilson-Bapu Effect completely naked.
LEONARD: Really? It doesn't read that way.
DR. PLIMPTON: Here, let me show you. (and drops her robe)
LEONARD: Wow. You really make science come alive.
Everybody wakes up in the morning, and Leonard and Elizabeth had more than a pleasant night...if the giggling is any indication. She'll have her coffee first, since hearing Sheldon in the bathroom put her off doing that. Penny stops by to request a ride to work because the engine light came on. The one that tells you to fill the car with gas. Leonard will take her, but she is introduced first to Elizabeth. Elizabeth says she was really enjoying her stay...and fortunately Sheldon inadvertently stops the moment from being awkward for long, as Leonard's bathroom time was coming up, and you really don't want to follow him. Leonard goes to get dressed but Penny stops him. A little jealousy about Leonard sleeping with Elizabeth seeps out, given that they just broke up. Sheldon is offended that Penny would suggest Leonard sleep with his "doctor buddy,"
PENNY: I'm not suggesting it, I'm saying it happened.
LEONARD: It wasn't my fault.
SHELDON: What, did you accidentally trip and fall into 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.
SHELDON: She's my friend. And you are playing with her!
LEONARD: (to himself) Yeah, I guess I did.
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 with Raj. For proof, we go to later on with Elizabeth and Raj at his apartment. Howard brings over soup thinking Raj is still sick, and Raj tries to send him away, since he's loopy on Ny-Quil. However, Elizabeth wants Howard to stay for some role-playing games. And not the kind that required a 12th-level dungeon master.
ELIZABETH: You two work out the details while I change into something I don't mind you ripping off my milky flesh.
RAJ: Will you go! She wants New Delhi, not Kosher Deli! You have a girlfriend!
HOWARD: I broke up with her weeks ago! I was waiting for the right time to tell you. And this IS the right time!
And Leonard arrives, making it even more fun for Elizabeth. Now it'll be a foursome.
HOWARD: Welcome to the Penthouse Forum.
Realizing they'd all be naked in front of each other, they decline. And then Elizabeth shows up in panties and a bra. (and looking good, too. Kudos to Ms. Greer.) Raj suggests they go outside to make a dramatic entrance. Howard and Leonard do...and get locked out.
RAJ: So you say you can't pay your rent...
Not only does Leonard lose something special, he has to walk upstairs with Penny, who is still giving him grief about Dr. SlutBunny. He wants to explain why he did what he did.
LEONARD: She let me.