The Big Bang Theory was on the air for 12 seasons, becoming a big winner at the Emmys and a favorite among its loyal fans. It has become one of the longest-running sitcoms in television history. During its long run, the cast developed their own favorite episodes and guest stars. There is a lengthy list of guest actors who have appeared on the show.

However, just because there were so many actors who made guest appearances on the show, it doesn't mean they all played one role. In fact, there was one actress in particular who played two different characters on the show during its run.

'The Big Bang Theory' Cast Chose Their Favorite Supporting Player On The Show

As The Big Bang Theory was ending its run in 2019, the cast reflected on the show with USA Today. The cast were asked to pick their favorite supporting player during the show's 12-season run. For starters, Mayim Bialik chose Kevin Sussman, who played comic book store owner Stuart.

"He's part of our family," Bialik said. "I learn a lot from him as an actor. He does a lot with a little and he has an understated way of handling things that otherwise could be too much."

When Jim Parsons was asked to choose his favorite, he couldn't pick just one. He chose Laurie Metcalf and Christine Baranski, who played the mothers of Sheldon and Leonard.

"I see them as actor's actors," Parsons said. "All the years that I watched them (before Big Bang), I would identify with them as performers, as a fellow craftsman in the field. To meet them and realize that was true was overjoying. Working with them was as rewarding and interesting as I always thought it would be."

When it was time to choose their favorite guest star, Simon Helberg chose Stephen Hawking.

"That's a moment where I was looking at him and I just couldn't process that he was here," Helberg said.

"It's those moments that do tend to be larger than life."

Melissa Rauch said that her favorite guest star was Bob Newhart.

"I've been such a big stand-up comedy fan my whole life," she said. "I had a Bob Newhart record album as a kid that was my father's (and) I did stand-up before I came to (Big Bang). I had a wonderful conversation with him about stand-up and the live audience aspect and our love for it. I will cherish that conversation always."

The Cast Chose Their Favorite Episodes During The Show's 12-Year Run

The cast also chose their favorite episodes while speaking to Entertainment Weekly.

Kaley Cuoco said her favorite episode was "The Bath Item Gift Hypothesis."

"My favorite episode will always be the Christmas episode when Penny gives Sheldon a napkin signed by Leonard Nimoy," she said. "Sheldon is so overwhelmed with emotion he proceeds to hug Penny for the first time ever! I think Jim and I had our own set of secret tears flowing."

For Johnny Galecki, it was "The Recombination Hypothesis."

"'I love when Leonard has his fantasy date with Penny," he said. "It could have been a real departure for the show, and it took a lot of courage on the part of the writers, who thought we could do it and still have it be on The Big Bang Theory.

"

Bialik and Rauch both chose "The Countdown Reflection."

"That episode was fun and emotional, not only because we were cataloguing a huge shift in all the relationships between all the characters in the show but it was a week during which we, the cast, got to spend pretty much every scene together," Bialik said. "That made for a great way to end a great season."

"The closing scene where we are all sitting on the couch watching Howard launch into space was extremely special," Rauch said. "I thought it was so beautifully written.

Our writers are hilarious and infuse each scene with so much laughter, but they also don't shy away from the heart — that scene being a perfect example."

Molly Morgan Played Two Different Roles On 'The Big Bang Theory'

During the 12-season run of The Big Bang Theory, many different actors have appeared on the show. However, not all of those actors have stuck to playing just one role. In fact, actress Molly Morgan played two different roles during the show's run.

She first appeared as one of the Goth girls that Howard picks up as a date in the episode "The Gothowitz Deviation.

" Morgan showed up again as a creepy hostess of an escape room the gang tires out in the episode "The Intimacy Acceleration."

Helberg didn't choose either one of these as his favorite episode, however. Instead, he chose "The Werewolf Transformation."

"I thought that episode so purely represented our show," he said. "Sheldon deals with needing a haircut while his barber is in the hospital, and Howard explains his grueling astronaut training via Skype to Bernadette. Nothing fancy. Just these richly layered characters having human moments with each other."

When speaking to Entertainment Weekly, Cuoco reflected on how the show's live audience changed over the years.

"These audiences are insane," Cuoco said. "Their energy is high. I don't know how it works [to get them here]. It's like Hunger Games. They wait a long time to come. I'll read comments on my social, and I'll come across one that says, 'I have tickets for a 2019 episode.' They've had them for years. I don't think there will be anything like a Big Bang audience taping ever again. Our audience is unbelievable."