He also hosted the long-running syndicated talent show Star Search, and performed in television commercials.
McMahon has appeared in several films, including The Incident (1967), Fun With Dick and Jane (1976), Full Moon High (1981) and Butterfly (1981).
During World War II he was decorated as a Marine fighter pilot, and continued his military career in 1952 by flying 85 missions in Korea.
In 1986 "Weird Al" Yankovic wrote a tribute song titled "Here's Johnny".
From 1997 to 1998 he appeared in the situation comedy The Tom Show.