Rogaine is really a satire derivative work and not a parody. To be a "fair use" parody, you have to somehow comment on the original work that you are copying from.

Quote:

Producers or creators of parodies of a copyrighted work have been sued for infringement by the targets of their ridicule, even though such use may be protected as fair use. These fair use cases distinguish between parodies (using a work in order to poke fun at or comment on the work itself) and satires (using a work to poke fun at or comment on something else). Courts have been more willing to grant fair use protections to parodies than to satires, but the ultimate outcome in either circumstance will turn on the application of the four fair use factors. -- http://en.wikipedia.org/wiki/Fair_use#Fair_use_and_parody />