"The Big Bang Theory" followed rigid guidelines throughout its 12-season run, including a unique rule on the appearance of its male characters: Sheldon, Leonard, Howard, and Raj. The creators aimed to maintain a consistent look for the protagonists, even discouraging them from sprouting beards or facial hair. Fans observed the actors would often grow beards during filming breaks, showing their preference, which however did not fit into their characters' on-screen portrayals. Wardrobes remained unchanged as well, reflecting each actor's distinct style. Interestingly, Johnny Galecki, who played Leonard, successfully insisted on wearing glasses constantly, despite initial reservations from the producers. The glasses, though causing filming issues due to lens glare, were retained after Galecki cleverly removed the lenses. Another unwritten rule was sticking to the script, with scope for improvisation limited due to the high caliber of the writing team and the tight production schedule. This ensured smooth execution of the show's 279 episodes.