The Big Bang Theory Recap: Knock 3 Times

The Hot Tub Contamination
Kaley Cuoco as Penny, Johnny Galecki as Leonard. Photo: Sonja Flemming/CBS
The Big Bang Theory

The Big Bang Theory

The Hot Tub Contamination Season 10 Episode 5
Editor's Rating 4 stars

Important stuff happens in this week’s episode, but all that will have to wait … because we found out the backstory behind a trademark Sheldonism!

Learning why Sheldon knocks three times on any door before entering is such a major reveal that Penny’s maiden name, Howard’s dad, and the birth of Baby Wolowitz can’t be that far behind. And it turns out that the aforementioned backstory is not only sad, but it also involves an early character-defining moment for Sheldon.

While he and Penny are at an ice-cream parlor, where he insists he’s going to hit on other women after new roommate Amy refuses to adhere to his bathroom schedule, Sheldon tells Penny he wants to share a secret he’s never told anyone.

When Sheldon was 13 and on spring break from college — he was sent home early because they ran out of math to teach him — he entered his house in Texas, thinking it would be empty because his mother was at Bible study. But he heard a noise coming from his parents’ bedroom, and when he opened the door, he found his father “having relations” with another woman.

“It’s why I never open a door without knocking three times,” Sheldon explains. “The first one’s traditional, but two and three are for people to get their pants on.”

He and his father locked eyes, Sheldon ran to his room, and the two never spoke of what he saw. It still haunts him, though, and he tells Penny that since he and Amy started living together, they’ve been bickering the way Mama and Papa Cooper used to. Sheldon worries that means he’ll end up doing something hurtful to Amy like his father did to his mother, so he concludes he may as well start hitting on women at the ice-cream shop, since he’s going to be unfaithful like his dad was.

Penny, of course, points out how silly that logic is, and suggests he instead be more concerned with behavior that’s hurting Amy right now — like bickering with her, refusing to share a toothbrush holder with her, and threatening to see other people because she won’t sync up her potty time with his. Yet another example of why, ultimately, Penny and Sheldon’s friendship may end up being the most honest and entertaining one of the series.

Back home, Amy spends the afternoon being counseled by Leonard on the ways of co-habitating with Sheldon. Amy and Leonard make for another pairing that, while rarer, is also always good for laughs and an insight or two. When Sheldon and Penny return, he immediately — well, immediately after sitting in his spot on the couch and noting that it’s warm, indicating someone else dared to occupy it — apologizes to Amy for his bathroom-schedule hissy fit, and tells her he’s even ready to take their relationship to the next level.

Yes, he sweetly (and as Penny points out, oddly romantically) asks Amy to share a toothbrush holder with him. She says yes, they plunk their pink and blue brushes into the ceramic container, and hug.

Yep, no one ever said it was going to be easy — Penny and Leonard warned it would be anything but, in fact — but Sheldon has reached the point where he’s learning to be a giving, compromising partner for the sake of his relationship with Amy. Given how consumed he’s become with their relationship and its future in just these last two episodes, the not-too-distant future is looking more and more like Amy Farrah Fowler will become Amy Farrah Cooper.

As for the rest of the gang, Bernadette (whose tummy is finally beginning to look progressively pregnant) and Howard learn they have a big problem. It boils down to this: There are way too many copies of their house key.

When Bernie’s morning sickness prevents her and the hubs from going on their planned Palm Springs getaway, they decide to enjoy a relaxing staycation without telling their friends. That means Raj and Stuart think they’re out of town, which is why they both end up sneaking into Casa Wolowitz to enjoy the backyard hot tub. At first, Bernie and Howard think someone is breaking into their home, and when they realize it’s just their moocher friends, they crack open the window and listen in to the conversation. The big news: Raj went from having two girlfriends to having no girlfriends. He and Stuart discuss his love life, or lack thereof, while they’re sharing the hot tub. Raj had kept his relationship status from his friends, but turns out both Emily and Claire broke up with him, and he says he’s bummed about it. Is that why he kept it secret? Is the fact that all his friends are settling down and beginning to have babies making Raj anxious about his own future? Is Raj, the guy who wants to get married and have a family probably more anyone else in the group, doomed to remain the single friend?

All good questions, if I do pose them myself, but ones that must take a backseat to more pressing concerns. While Raj entered the hot tub with swim trunks on, Stuart took a right turn at Albuquerque — and a naked Stuart enjoying the jet-propulsion relaxation of his home spa is just a little more than Howard Wolowitz can stomach.

“You jackasses should buy yourselves a hot tub!” he yells out the window, bringing an official end to Raj and Stuart’s tub time, and, just guessing, their possession of Wolowitz house keys.


  • Sheldon: “Oh, look who’s in favor of compromise: the woman who married Leonard Hofstadter.” Leonard: “Hey, she didn’t compromise, she settled. There’s a difference!” Penny: “You tell ’em, babe.” As tired Penny-married-beneath-her jokes go, this is one of them.
  • Chuck Lorre’s best vanity note ever: “A Nonpartisan, Nondenominational Prayer for America: God, please make this election be over soon. Amen.” Amen!

The Big Bang Theory Recap: Knock 3 Times