Conversation so far:
What did Art Donovan do when he left the nfl?
He published an autobiography, Fatso, in 1987.
Was Art Donovan's autobiograpghy a hit?
What did Art Donovan do after the autobigraphy was published?
Donovan also appeared ten times on the Late Show with David Letterman
Did Art Donovan ever become a sports announcer?
He appeared as a guest commentator at the WWF King of the Ring tournament in 1994.
What kind of television and speaking appearances did Art Donovan make?
Donovan guest-starred in the Nickelodeon show The Adventures of Pete & Pete in the episode Space, Geeks, and Johnny Unitas.
When did Art Donovan retire?
08/30/1962
What shows did Art Donovan do besides Letterman and WWF?
Donovan also made several appearances on The Tonight Show Starring Johnny Carson.

Question: Was that a one time guest appearance or multiple shows?
Self-contained rewrite: Was that a one time guest appearance or multiple shows?