Conversation so far:
What lead The Mothers of Invention to get back together?
Later in 1970, Zappa formed a new version of the Mothers (from then on, he mostly dropped the of Invention).
What was the connection between The Mothers of Invention and Flo and Eddie?
Mark Volman and Howard Kaylan, who, due to persistent legal and contractual problems, adopted the stage name The Phlorescent Leech and Eddie, or Flo & Eddie.

Question: What film were they involved in?
Self-contained rewrite: What film were The Mothers of Invention in?