William Christopher contracted an almost fatal case of hepatitis at the start of the fifth season, resulting in his having to miss several episodes. As a result, producers were planning to write Father Mulcahy out of the show. However, Alan Alda pushed to keep him on the series, knowing how dependent Christopher was on needing steady work to help raise his autistic son. Alda went as far as writing an episode to incorporate Christopher's real-life illness into Mulcahy, helping to convince producers to keep him on the show.
Klinger often mentions a restaurant in his hometown of Toledo, Ohio called Tony Packo's, specializing in Hungarian hot dogs. This is a real restaurant on Toledo's east side that is still popular with many who live in Toledo and the surrounding area.
Radar's teddy bear, once housed at the Smithsonian, was sold at auction July 29, 2005 for $11,800. It was originally found on the Fox Ranch, where the series was filmed, and became part of the show.
The dog tags worn by Jamie Farr on the show were his own personal dog tags from when he served in the military prior to becoming an actor. In one of the archival interviews found on on the extras DVDs in the Medicine and Martinis box set of the show, Jamie Farr stated that they are his own tags with his actual personal military information, including name, serial number, and religion.
Klinger (Jamie Farr) was only going to appear in one episode. However, he proved to be so popular that he became a regular.