"The Big Bang Theory" had one strict rule for its male characters Sheldon, Leonard, Howard, and Raj across its 12 seasons: no facial hair. Fans spotted this consistent style element alongside strict adherence to the scripted lines. The actors, including Simon Helberg, Kevin Sussman, and Kunal Nayyar, all praised the quality of the writers and noted that improv was of little necessity. The adherence to a uniform look and script was born out of a need for smooth production in a tight shooting schedule, according to reports. However, some modifications were allowed. Johnny Galecki, who played Leonard, insisted on his character wearing glasses, despite initial pushback from the producers. His persistence paid off, the glasses remained and became an iconic part of his character's appearance. Galecki revealed that he wore the glasses during the rehearsals, and when asked to take them off for the shoot, he refused, saying he intended for Leonard to wear them.