Messing, who previously starred on Will & Grace, can be seen in Smash, the NBC series that revolves around a musical based on Marilyn Monroe.
"Every week, we would be called together as a full cast to read the next week's script, and every week inevitably I would exclaim in the middle of the reading, 'Oh my God, are you kidding me?' because there would be some revelation that was completely unexpected, and everyone would laugh, and it became like a running joke," she told Elle magazine.
"That's kind of one of the wonderful things about television, the thing that makes television terrifying. It's something that Uma Thurman and I spoke about because it was the first time she had done television. She was like when you're in a film, it's a finite thing, it's a two-hour story, you know how it ends, and you can craft your character, you have all the information.
Messing added: "In television you only have the information that's been given to you so far, and at any moment your character can become something completely opposite from what you thought it was. That requires a completely different kind of muscle, and I think it's exciting."
Messing previously talked about her wardrobe in Smash, describing it as creative but practical since her character is both a mum and the musical's co-writer.
Thurman is set to sing and dance as Monroe in an upcoming Smash episode.
Watch a trailer for Smash below: