With a long history and a dedicated fandom, The Big Bang Theory continues sparking conversations among fans years after it went off air.

However, even the most dedicated viewers might not know all of the behind-the-scenes secrets from the beloved sitcom.

For instance, did you know that Sandra Bullock was supposed to appear on the show? Her role went to another very popular actor after it didn’t work out.

Revolving around Jim Parsons, Kaley Cuoco, Johnny Galecki, Simon Helberg and Kunal Nayyar, so much happened onscreen, but it turns out that just as much was going on when fans weren’t watching.

We did some digging and rustled up 12 facts about the show, including details about guest stars who turned down roles (that list includes a massive pop star), actors who were almost overlooked, onset romances, future plans for reboots and more.

Take a look and let us know what, if anything surprised you!

Scroll through the slideshow to check out 12 big secrets from the set of The Big Bang Theory…