If you enjoy Calvin and Hobbes for its humor, wisdom, and the interaction between a boy and his animal, you'll surely enjoy Copper. This beautifually drawn book of short but poignant comic strips is, in my mind, a masterpiece. Follow Copper and his dog Fred through all sorts of imaginative journeys. Fred is nervous and scared, while Copper is curious and ready to explore. These two personalties play off one another perfectly through adventure after adventure.
If you're ready for a more grown-up comic, but still one that's childish and wholly appropriate for all ages, check this out.