1- Penny’s last name was never revealed throughout 9 seasons of the show.
2- Mayim Balik (Amy) is a successful neuroscientist in real life and not just in the show.
3- Most music playing scenes are real where many of the actors play different instruments in real life:
-Johny Glaceki plays the cello.
-Jim Parsons plays the piano.
-Mayim Bialik plays the harp.
4- The show was copied in Belarus, but it did not last when the channel that was airing it discovered the replication. The characters names were: Sheldon, Leo, Hovart, Raj, and the waitress Natasha.
5- There is a new bee species and a new jellyfish species that was named “Bazinga” honoring Sheldon’s character.
6- Jim Parsons never watched any of what is claimed Sheldon’s favorite TV shows like Star Trek and Dr. Who.
7- Amy’s real name “Mayim” was mentioned in one of the early episodes as a smart woman that was going to compete against Sheldon’s team in one of the games. Two years later Mayim joined the show as Amy.
8- All stairs’ climbing scenes were filmed on one floor where the same scene was repeated to look like they are on different floors.
9- The song “Soft Kitty” is a real song from 1930 and it was called “Warm Kitty”.
10- Sheldon’s name was going to be “Keny” initially.
11- All the males except for Howard have seen Penny naked. (He probably planted cameras all over her apartment lol).
12- Kate Miuccia who played Raj’s girlfriend Lucy was going to play Amy’s role initially.
13- Sheldon’s outfits reflect the mood, red for anger, blue for hope etc.
14- Parson (Sheldon) and Cucco (Penny) are the highest paid actors ever, they made $29 million and $28 million annually respectively toping Ashton Kutcher who made $26 million on “Two and a Half Men”.
15- Raj’s silent shy character towards women is inspired by a real man named Red Person.
16- Penny and Leonard dated in real life, and despite their marriage in the show they broke up in reality after a two years marriage.
17- The names Sheldon and Leonard were derived from the famous director and photographer “Sheldon Leonard” who is considered the inspirer for the directors of the show.
18- The show started initially with different actors, but the channel that was airing it thought that different actors would bring more revenue and which what happened.
19- Leonard and Lesly worked before in a show called TV Blossom.