Garfield is a comic strip by Jim Davis, who seems like a pretty good guy.
A Markov chain is a probabilistic model well suited to semi-coherent text synthesis.
Garkov is an application of the Markov model to transcripts of old Garfield strips, plus some extra code to make it all look like a genuine comic strip. Feel free to screenshot and share Garkov output.
Josh Millard is responsible for this mess; he also has a blog and frequently does stuff. His current comic project is Larp Trek, in which the crew of Next Generation plays a roleplaying game called Deep Space Nine.
Other people have made weird Garfield-related things, including: Garfield Minus Garfield - Lasagna Cat - Garfield Variations - Barfield - Permanent Monday - Arbuckle - Garfield Randomizer - The Death of Garfield - Nothing Garfield - forum weirdness - Garfield's Comic Creator - Garfield Generator 2
Some further reading: Comics Curmudgeon on Garfield - Comic Strip Doctor: Recontextualization - Comic Strip Doctor: Garfield - Newspaper Comics and their Enemies