The former Will & Grace star recently joined comedy Party Down to fill the gap left by Jane Lynch, who plays Sue Sylvester in Glee.
"I mean, they never offered me [a guest star role in Glee], but if they did, I'm sure I would do it," Mullally told TV Squad. "It seems like it would be a blast to do."
She continued: "I know that there's two ways to go, because they're probably aware that I sing. So that's one way to go, and then the other way to go is to do something with Jane - just play some, like, crazy nemesis of hers or something. I love her and I love working with her too. She's awesome."
Mullally also revealed details of Lynch's return to Party Down.
She said: "Jane Lynch is going to come back as her character from the first season, and she's marrying this brilliant older guy, this much older man, and they're having a very new age wedding. So she's wearing these flowing garments, and there's a lot of beads and a lot of scarves, and she's really chill and it's really funny."
The second season of Party Down premieres tonight at 10pm on Starz.