http://splitsider.com/2013/08/america-meets-letterman-and-keaton-on-a-failed-mary-tyler-moore-variety-show

Both were stars of "Mary," which ran in 1978, one year after "Mary Tyler Moore" ended.
Read more at http://www.hitfix.com/tv-tattle#EuGP44iKekAK1aMw.99

I'm surprised Mary's variety show wasn't a hit, seeing as variety shows were all the rage at the time, Mary was a known commodity and that she was no slouch in the singing and dancing department. She'd try the format again (and fail again) with The Mary Tyler Moore Variety Hour in 1979.

If you want to know why it failed, watch Letterman sing and dance.

Dave's worst nightmare revisited.
(From "Late Show," air date: 4/28/15)

Michael Keaton and Dave Sing & Dance With Mary Tyler Moore | David Letterman (https://www.youtube.com/watch?v=tv8hm94pEbU)

tv8hm94pEbU