I stumbled on this site the other day (thanks to that amazing machine of sharing now called twitter). Evidently, Ryan Dunlavey has been doing these mash-ups for a number of publications. He is the co-creator of Action Philosophers by Evil Twin Comics.
His recent blog post includes his entire cartoon mash-up collection where he takes our most popular sci-fi, cartoon and fantasy characters and puts them into standard old-newspaper comic strips. The results are hilarious. Think "X-men meets Peanuts" and the wonderfully titled "Spy vs Spy vs Alien vs Predator".
