The documentary explores the enigmatic life and music of Harry Nilsson in a attempt to answer the question,"Who's Harry Nilsson?" The film comprises and movie such as interviews with Robin Williams, Yoko Ono, Van Dyke Parks, Randy Newman, Ray Cooper, the Smothers Brothers, and Micky Dolenz. "Who's Harry Nilsson?" Uses home pictures, music videos, and films. Segments from the documentary made through the record of Son of Schmilsson (Did Someone Drop His Mouse?) . And excerpts from Nilsson's rare TV looks in his BBC specials, the"Smothers Brothers Comedy Hour","Playboy After Dark", and in a event of"The Ghost and Mrs. Muir".