Ever since The Big Bang Theory first debuted in 2007, fans have wondered why Sheldon Cooper knocks three times on a door before entering a room. Well, during Monday's episode, that question was finally answered.
Knocking three times in a row is one of Sheldon's many quirks, and the reason behind it is actually quite heartbreaking. In a confession to Penny, Sheldon explained that when he was just 13, he walked in on his dad having sex with another woman while his mom was at Bible study.
Since that devastating moment, Sheldon now knocks three times just to make sure he's not walking in on something that he shouldn't see, doesn't want to see or something that will upset him. As he told Penny, "The first one's traditional, but two and three are for people to get their pants on."
As annoying as Sheldon can be sometimes and whether or not you consider yourself a fan of his, there are times that he's relatable. Occasionally, he opens up about why he is the way he is or confesses something about himself he may be ashamed about. Those are the moments you can't help but sympathize with him.
Like with the knocking, there have been several other times when Sheldon has let others in. It's always interesting to learn more about him and why he is the way he is because he is such a unique and sometimes guarded character. With that, here are a few moments when we've gotten to know more about Sheldon as both a character and a person.
In Season 9, Sheldon showed Amy his secret storage locker where he has kept every single thing he's ever owned, including old toothbrushes. It's something he's never told anyone and is ashamed of, so it was surprising to see him make such a confession to Amy. Of course, she made the situation better by not judging him and letting him know that whenever he wants to possibly throw some things out, she'll be there.
Sheldon's never been a physical or intimate person, but that all changed when he and Amy finally had sex for the first time. Though, one of the more eye-opening moments was before they consummated their relationship. Sheldon let his guard down and explained to Penny that he's always been uncomfortable with any type of physical contact, including just a handshake. Then, he even admitted that there was a possibility he would one day have sex with Amy. This was one of Sheldon's huger moments.
It's no secret that Sheldon hates Christmas and his hatred was finally explained in Season 6. Apparently, when he was a little boy, Sheldon asked Santa to bring back his grandfather (aka "Pop-Pop") who had just died that same year because he missed him. However, Santa didn't do that, and Sheldon has never looked at Santa or the holiday the same way again.
While asking each other questions to get to know each other better, Sheldon revealed the one ability he'd want to have. He wished he could read minds, so he wouldn't feel so out of the loop about how people are feeling, what they really mean or what they're trying to tell him. It's hard for Sheldon to understand emotions and social cues, which is why he'd want to be a mind reader — then he wouldn't feel so stressed about being around people.
Sheldon doesn't like presents, celebrations or surprises, which is why he was so against celebrating his birthday in the 200th episode. Before changing his mind and allowing Amy to throw him a party, Sheldon confessed that the reason he hates his birthday is because when he was younger all of his twin sister's friends would tease him constantly at their party. He also admitted that people he invited would never show up, but that didn't bother him so much, unlike being tortured by his sister's friends on his birthday.
Over the course of 10 seasons, fans sure have learned a lot about Sheldon Cooper, haven't they?
The Big Bang Theory moves to Thursdays at 8/7c on CBS starting Oct. 27.
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