Penny suddenly became a bartender 0n season 4 due to an unfortunate event involving Kaley Cuoco in real life. Before she became a successful pharmaceutical sales representative, the character was an aspiring actress who moved to California from Nebraska.

Penny was the only one who wasn’t in the scientific field. That makes her more aligned with the viewers’ perspective within the show, as Leonard Johnny Galecki and Sheldon Jim Parsons typically need to explain to her what they do for a living.

The change in Penny’s job was motivated by an unfortunate accident. As she recalled in an interview in 2010, her horse was spooked during a riding lesson and it caused her to fall off of it.

Penny’s interactions occurred while she was manning The Cheesecake Factory’s bar. A couple of times throughout this whole duration, Sheldon reached out to her for advice.