Originally Posted by Toonlogos

These can really be classified as parodies, such as found in MAD magazine, albeit much more sexual in nature, and therefore exempt from copyright suits.

To quote -

"A parody exists when one imitates a serious piece of work, such as literature, music or artwork, for a humorous or satirical effect. A parody must inevitably make use of another creative work. This inherently creates a conflict between the creator of the work that is being parodied (as no one likes to be criticized, made fun of or ridiculed) and the creator of the parody. It is also highly unlikely that a copyright owner will grant permission or a license to a parodist to use their copyright protected work in creating a parody. Hence the parodist has to rely on the fair-use defense to forestall any liability for copyright infringement."