Janney played Crystal in the comedy, which was axed by ABC earlier this year after one season.
Janney has now told The AV Club that she enjoyed working on the show.
"I mean, it was just a candy store for me," she said. "I had so much fun playing her, and I wish I could've gone on playing her, because she was really fun. I love to play those absurd women. And I got to sing with James Taylor! If nothing else, I got to do that."
She added: "I had a great time. I'm sorry and sad it didn't go, but geez, I'm glad I got to do that."
Janney also praised her co-star Matthew Perry, who executive produced the show, and described him as "pretty great to work with".
"I applaud him," she said. "He was wearing so many hats. I could see it was exhausting him and yet he really cared about this, and really put his heart into it. I just admire him for it and applaud him. I could never do it in a million years, so I think it's admirable. He really held it together and did it, writing and rewriting while we were doing it. He did a great job. I'm proud of him."
Watch a clip of Allison Janney in Mr Sunshine below: