Maxwell's film debut was in the acclaimed 1974 Mel Brooks comedy film Young Frankenstein. He played one of the title character's medical students.
He was also featured in the 1977 Sketch comedy film Kentucky Fried Movie in a solo scene titled "Feel-A-Round." The box-office success was directed by John Landis and written by Jim Abrahams, David Zucker and Jerry Zucker, who subsequently wrote the classic film comedy, Airplane!.
In 1997, his cookbook, inspired by years of playing a mess hall cook on M*A*S*H, titled Secrets of the M*A*S*H Mess: The Lost Recipes of Private Igor, was published and he made an appearance on NBC's Today Show to promote it.
Maxwell is a regular participant on the alt.tv.mash newsgroup where, along with series Writer Larry Gelbart (up until Gelbart's death in 2009), answers fan questions about the behind-the-scenes workings of M*A*S*H.