The Big Bang Theory started out with five main cast members before adding several more, one of whom was originally meant to be a fleeting guest star.

It stars Jim Parsons as Sheldon Cooper, Johny Galecki as Leonard Hofstadter, Kunal Nayyar as Rajesh Koothrappali, and Simon Helberg as Howard Wolowitz. As the show progressed, many new characters joined the main cast.

Over the course of its 12-season run, The Big Bang Theory evolved from a quirky, niche sitcom about a group of geeky scientists into a bona fide pop culture phenomenon. The show’s unique blend of highbrow science references,