For fans of "The Big Bang Theory," Penny was a bubbly, personable foil to her nerdy neighbors, not to mention an accessible point of entry for those non-physicists among us. However, events unfolded off-screen that would ultimately shape Penny's on-screen arc.
At the beginning of the series, Penny is working as a waitress at The Cheesecake Factory while pursuing her acting career, but Season 4 saw her getting a different job at the restaurant. In a 2010 interview, Cuoco revealed that her character was suddenly switched from waitress to bartender due to a real-life horse-riding accident.
After the accident, Cuoco returned wearing a full leg cast, and the show's writers decided to stick the actress behind the bar, which provided the opportunity for some new comedic bits. Cuoco seems to have avoided any more horse-related injuries, which is for the best, especially considering it would be hard to hide behind a bar on her current show, “The Flight Attendant.”