Conversation so far:
How many celebrities did she have on her show?
CANNOTANSWER.
Was he the only celebrity on her show?
Taylor.
Did the celebrities do anything special for her show?
Winfrey sat down with Michael Jackson for what would become the most-watched interview in television history.

Question: When was Michael on her show?
Self-contained rewrite: When was Michael Jackson on The Oprah Winfrey Show?