Conversation so far:
Tell me something about Harry Nilsson's legacy?
Nilsson is the subject of a 2006 documentary, Who Is Harry Nilsson (And Why Is Everybody Talkin' About Him)?
Who produced the documentarty Who Is Harry Nilsson (And Why Is Everybody Talkin' About Him)?
The documentary was produced by David Leaf and John Schienfeld.

Question: What was the documentary about?
Self-contained rewrite: What was the documentary Who is Harry Nilsson (And Why Is Everybody Talkin' About Him)? about?