Working on The Big Bang Theory proved to be a smooth ride for so many of the guest stars on the show. Among the very top throughout the seasons was Kevin Sussman, who arguably became a regular on the show. Sussman praised the cast and those behind the scenes, calling it a breeze to work on given the easy-going nature of everyone behind the scenes. Brian Thomas Smith was another guest star that agreed with Sussman, stating that the main cast was always a joy to work with.
As for Charlie Sheen, it seems like his brief experience on the show was a different one. Although he did how have praise for the cast, he completely ripped the show and those in charge creatively. It should be noted that those words also took place during his public spiral.
Sheen said at the time about The Big Bang Theory, "I'm sorry, but Big Bang Theory is a piece of s*** – it's a stupid show and it's just lame, about lame people."
"I like the kids in it, but that show without us as a lead-in is… goodbye. And I'm rooting for those kids, because I know who they're dealing with. The fact that they're still sane is crazy. You know? He's a bad man. And I've backed off from him for a while."
At least he likes the kids...
Lio Tipton took part in The Big Bang Theory in multiple instances. In truth, fans likely didn't notice given how different she looked in both roles. One of them takes place in season 2 as a model, while her return doesn't take place until season 9, having an encounter with Sheldon and sporting a completely different look with short hair. She played the roles of Analeigh Tipton and Vanessa Bennett.
Tipton was especially remembered for her first time on the show. However, according to Metro, the episode did not sit well with everyone. The nature of it all was quite bizarre with Howard and Raj getting into her home.
The publication writes, "Howard Wolowitz and Raj Koothrappali finding their way to the America's Next Top Model house. The scientists pretended they were there to fix the cable, and got welcomed into the house – with the whole thing never mentioned again."
In her second appearance, things don't end all that well for Tipton who gets the door slammed on her face by Sheldon despite being her perfect match... Still, it shows the great versatility of the actress, who played two completely different roles.
Molly Morgan is another actress that got to play two different roles on the show. Her first took place as a Goth girl, getting picked up on a date by both Howard and Raj, which of course, doesn't end well for the duo. She returns as a host for an escape room in the later seasons as well.
Kate Micucci also factors in. The actress actually got her start on Big Bang behind the scenes working on a musical theme for Howard on the show. She spoke about getting the gig, "Steve Molaro called us. It seemed our music/comedic sensibility lined up with the show. Also, both Riki and I are huge fans of the show and have both been on it, so we were excited to write a song that was funny but also had a lot of heart."
Later on, Micucci transferred her skills to the actual show, playing the role of Raj's brief love interest. It just goes to show the great versatility of the actress and creator who was able to pull off completely different roles on the show. She was also rumored to potentially be in the running for Amy, but that eventually went to Mayim Bialik.