Kaley Cuoco was in The Big Bang Theory from the get-go, and despite there being 279 episodes in the series, she can easily pinpoint her favorites. As the only female character from the original cast, Penny appeared in all twelve seasons of the CBS sitcom. Throughout that time, she went through personal and professional growth — the show ending with her expecting her first baby with Leonard (Johnny Galecki) and excelling in her career.
Premiering in 2007, the show ran for 12 seasons until The Big Bang Theory finale aired in 2019. It wasn't always the hit that it eventually came to be, however: the original formula in the pilot had to be reworked, and Sheldon (Jim Parsons) and Leonard are the only characters from the original concept that made it to the revamped version. From there, three more players were added — Penny, Howard (Simon Helberg), and Raj (Kunal Nayyar). That was the case until season 4 brought in Bernie (Melissa Rauch) and Amy (Mayim Bialik) as new series regulars; they eventually married Howard and Sheldon, effectively bringing them into the Pasadena gang.
When The Big Bang Theory ended its run, it became the longest-running multi-cam sitcom, beating NBC's Cheers. Given that, there's no shortage of episodes for choosing favorites. For Cuoco, however, she has two unforgettable outings in mind as her standouts. Speaking with TV Insider, the actress cited The Big Bang Theory season 2, episode 11 titled "The Bath Item Gift Hypothesis" as it's the first time Sheldon hugged Penny. In the holiday-themed offering, the socially inept genius was contemplating on what to give his neighbor, unsure of how much effort he needed to put into choosing her present. Underestimating her, Sheldon was stunned when she gave him a napkin used and signed by Star Trek’s Leonard Nimoy. He went all out with gift baskets to show Penny his gratitude, but sensing that it wasn't enough, he also decided to give her a friendly embrace. This was so out-of-character since Sheldon hated physical contact, but proved that he was immensely thankful.
Cuoco also named The Big Bang Theory season 7, episode 3 titled "The Scavenger Vortex" as a favorite. In it, the gang agreed to participate in Raj's scavenger hunt after blowing off his mystery dinner. While typical outings of the series involved two plots, this one only focused on one collective story which is exactly why it's so memorable for Cuoco. For the game, the leads were partnered up with each other, but the team-ups were quite odd: characters who normally didn't have anything to do with each other, like Amy and Howard, had to work together. In the end, it made everyone so much closer. What's weird is that this is more like the storytelling in The Big Bang Theory's earlier seasons. The main narrative almost always involved everyone. However, as the cast expanded, CBS had to find a way so that everyone could have their time in the spotlight.
Admittedly, The Big Bang Theory has had its serious problems, especially with regard to its brand of humor. Sometimes it can be sexist, racist, and overall offensive; this is why despite being so popular, there are also people who can't stand it. But, looking at Cuoco's selection of favorite episodes highlights that the show was at its best when it focused on the relationships among its characters.