I got a question for you: Trapper John, M.D. is an American medical drama television series and spin-off of the film MASH (1970). Pernell Roberts portrayed the title character, a lovable surgeon who became a mentor and father figure in San Francisco, California. The show ran on CBS from September 23, 1979 to September 4, 1986. Roberts played the character more than twice as long as had Wayne Rogers (1972 -- 75) on the TV series M * A * S * H.

Based on this passage, who played trapper john on trapper john md?
Let's think first:
To answer this question, we should know that: Pernell Roberts portrayed the title character, a lovable surgeon who became a mentor and father figure in San Francisco, California.
Therefore, the answer is Pernell Roberts.