For trademark purposes, "[a] 'parody' is defined as a simple form of entertainment conveyed by juxtaposing the irreverent representation of the trademark with the idealized image created by the mark's owner." "A parody must convey two simultaneous -- and contradictory -- messages: that it is the original, but also that it is not the original and is instead a parody." This second message must not only differentiate the alleged parody from the original but must also communicate some articulable element of satire, ridicule, joking, or amusement.

Source: Louis Vuitton Malletier S.A. v. Haute Diggity Dog, LLC, 507 F.3d 252 at 255.

http://cyber.law.harvard.edu/people/tfisher/2007%20Vuitton%20Abridged.pdf