I believe the reference picture was "fair use" as defined here:
http://fairuse.stanford.edu/Copyright_and_Fair_Use_Overview/chapter9/9-c.html#2 (next to bottom of page)
Fair use. A movie company used a photo of a naked pregnant woman and superimposed the head of actor Leslie Nielsen. The photo was a parody using similar lighting and body positioning of a famous photograph taken by Annie Leibovitz of the actress Demi Moore for the cover of Vanity Fair magazine. Important factors: The movie company's use was transformative because it imitated the photographer's style for comic effect or ridicule. (Leibovitz v. Paramount Pictures Corp., 137 F.3d 109 (2d Cir. N.Y. 1998).)
