Parody is perfectly legal even for comercial use, as you can see by the latest StarTrek/StarWars parody from Germany:

The title is a spoof on both StarTrek and StarWars:

StarTrek TOS is called "Raumschiff Enterprise" (Starship Enterprise) in German.
So (T)raumschiff Surprise would be "Dreamship Surprise"
"Periode I" instead of "Episode I" would translate to "First menstruation"

Mr Spock was called Mr Spuck (spucken = to spit)
Cpt Kirk was Cpt Kork (Korken = cork)

And of course the MAD magazine regularly prints parodys of the latest graetest TV or Cinema hits.

As long as you make a REAL artistic parody (And just not call it that way to cover your rear), this is covered by "kstlerische Freiheit = Freedom of art" in Germany, and I think is protected by "Freedom of Speech" in the US.

stahlratte