Sometimes you just have to let things happen and do their magic.

There's nothing we don't love about The Big Bang Theory. Somehow, we find a way to genuinely care about the weirdest group of friends with the most awkward social behavior ever.

Raj, Howard, Leonard and Sheldon have made us laugh, cry and cringe throughout all 279 episodes of the show. Considering that their personalities were anything but typical, it was surprisingly easy to get along with them.

We even learned to love the strangest parts of their characters. Of course, sometimes it was much harder, like with Howard in the early seasons.

Same with Sheldon here. He is really the one whose personality is made up of many different quirks and traits. But there is one iconic part of his generally bizarre behavior that fans love the most. Yes, it's the three knocks thing.

Sheldon has this ritual, when he knocks on any person's door three times and then waits for an answer. But as the show's producer Lee Aronsohn revealed, this was never even in the script.

In Jessica Radloff's The Big Bang Theory: The Definitive, Inside Story of the Epic Hit Series Aronsohn shared that it was an on the spot decision to make Sheldon knock three times instead of just one.

"It showed Sheldon's obsessive compulsiveness. People like that like patterns and structure, so we had some fun with Sheldon once that got established," he said in the book.

Yes, that little tweak to the script in season 2 definitely added some laughs to the show. But later, the writers decided to put a darker spin on it. Sheldon revealed in season 10 that the real origins of the habit came from his childhood.

When he was 13, he caught his father with another woman. From then on, he vowed never to walk into a room again. Oh, The Big Bang Theory, we just wanted to have a nice laugh…