Making Parody of common tv-series

hi

i´m planning to create (with a friend) a 3d-movie (about 3 minutes long). in this movie will fight homer simpson and mr burns in matrix-style (no senseless violence, no blood, its just a project for university).
the only actors are homer and monty (and they look really good :D), all other (the city-environment) is invented and made by us
the project will be released under GPL

i just want to figure out the legal situation.
does i have to consider something if we create this?

Sounds like a fun project!) You won't have to worry about anything long as you don't sell it. And include in the credits include who the characters really belong to like "©FOX and its related entities" or "Homer and Monty characters are based off of FOX original characters and belong to FOX" I know it's something like this but in different wording maybe.

or just email them and describe what your doing with it.

http://www.fox.com/corporate/terms.htm

its possible to get copyright problems since homer is as far as i now not gpl :-P
but you are allowed to sell it even though its gpl