TV shows have used famous people and other TV shows for years in their episodes. For example:
1. On "227", Marla Gibbs are her friends go to Hollywood to appear on "Wheel of Fortune". Pat Sajak and Vanna White played themselves.
2. On "The Odd Couple", Oscar and Felix go on "Password." Allen Ludden and Betty White played themselves.
3. Vanna White played herself and the high school test administrator on "Full House".
4. On "Good Times", there were plenty of references to politicians; movie, TV, and recording stars; and civil rights leaders.
5. In "American Graffiti", there were references to President Kennedy, Sandra Dee, and Connie Stevens.
6. In Grease, there was a song entitled "Look at Me: I'm Sandra Dee", with references to Doris Day, Troy Donahue, and Elvis.
There's nothing wrong with using famous people in fiction, as long as you don't defame their reputations. I was going to write a short story using Dr. Phil as one of the characters, but then I changed my mind and didn't do it; for fear that Dr. Phil might sue me. But like I said before: when in doubt; fictionalize.