The following is an expanded version of a post originally written on October 31st, 2012.
M*A*S*H had just one episode focusing on Halloween. It was “Trick or Treatment” from Season 11 (originally broadcast November 1st, 1982). The episode involved a dead soldier coming back to life, the doctors sharing ghost stories, and Charles dealing with a Marine who has a pool ball stuck in his mouth.
Hawkeye, B.J., Colonel Potter, Margaret and Klinger are all seen wearing Halloween costumes. Here’s a good shot of most of them:
Notice the characters in the background are also dressed up. A ghost can clearly be seen. A number of extras in other scenes are also shown wearing costumes. Here’s Klinger in his zoot suit:
The best part of this episode was Charles pretending not to notice that the poor Marine (played by George Wendt) had a pool ball in his mouth. The worst part? B.J.’s clown horn.