A Guide For The Married Man (1967)

Happily married Paul (Walter Matthau) discovers his buddy and neighbor Ed (Robert Morse) has been cheating on his wife.  Paul is curious -- a little too curious, in fact -- about how Ed has been able to get away with it for so long.  Ed makes the process look effortless, and it's not long before Paul is considering stepping out on his wife, Ruth (Inger Stevens).

Paul's decision seems kind of crazy, considering his wife is very personable and attractive.  Ed regales Paul with stories of how other guys have done it and how well or not they handled situations that came up.  The stories are presented in scenes featuring various actors in cameos, including Joey Bishop, Phil Silvers, Jayne Mansfield, Lucille Ball, Jack Benny, Ben Blue, Louis Nye, Sid Caesar, Terry-Thomas, Carl Reiner, Polly Bergen, Sam Jaffe, Hal March, and Marty Ingels.  Some of the stories are mildly amusing, others are more humorous.  The film goes along at a fast pace, leading up to Paul planning to have an affair with an attractive client.

Reportedly, this was the last film that Jayne Mansfield actually did before a fatal accident took her life.  In the version of this film that I saw, it appeared that the story Ms. Mansfield appeared in was edited.  Perhaps to cover up how much of herself she was showing; but by late 1960's standards in comparison to today, the scene is very tame.