Mistress: Mimi Machu (actress, dated mid- to late-1960s, while married to Knight)
Mimi and Jack began dating while he was still married to Sandra Knight. Their relationship also continued after the divorce from Knight.
Jack always gave Mimi at least small parts in movies he either starred in or produced at the time. She was often credited as I.J. Jefferson, instead of Mimi Machu, for some unknown reason. The movies she appeared in with Jack were "Hells Angels on Wheels" (1967), "Psych-Out" (1968), "HEAD" (1968), and "Drive, He Said" (1971).
Interestingly enough, in "HEAD," which starred The Monkees, there was a scene in which she kissed each of the members of the band. Her character`s name was Lady Pleasure. Hmm...
Rumor has it that Mimi broke off the relationship because of suspicions that Jack was cheating on the set of "Five Easy Pieces." He had this to say about the break up: "I had been with her for three years, in love. After she left, I couldn't even hear her name mentioned without breaking out in a cold sweat."