I don't think it was anyone well known. I was not a huge Cheers fan, but the scene is hilarious. Lilith refers to the first wife as "Nanny G Spot" and while the women are slugging it out, Frasier tells Sam that it's the proudest moment of his life, or something like that. Kelsey Grammar has a real gift for delivering his lines....
Emma Thompson played Nanny G
Emma Thompson - I looked it up....