One wonders if, next to the departments Marketing and Human Resources, there are a number of offices marked “Industrial espionage” in the studios of Pixar, Dreamworks and other animation houses. It could be a coincidence, but they seem to do the same kind of movies at the same time:

Ants: A bug’s life (Pixar – 1998) | Antz (Dreamworks – 1998)
Monsters: Monsters Inc (Pixar – 2001) | Shrek (Dreamworks – 2001)
Oceans: Nemo (Pixar – 2003) | Shark’s tale (Dreamworks – 2004)
Wild animals: Madagascar (Dreamworks – 2005) | The Wild (Disney – 2006)

Hyperactive nut-focused squirl-ish creature:
Ice age
Ice Age II (Blue Sky – 2006)
Over the hedge
Over the hedge (Dreamworks – 2006)

Rats:
Ratatouille
Ratatouille (Pixar – 2007)
Flushed away
Flushed Away (Dreamworks – 2006)
(Actually there are even more rat movies: Ratatouille, Flushed Away, Rats Amore and One Rat Short)

Pinguins:
Surf's Up (Sony 2007)
Surf’s Up (Sony Animation – 2007): pinguins
Happy Feet (Warner Bros 2007)
Happy Feet (Warner Bros – 2007): pinguins (check this one, great trailer!)

Martial arts chubby animals:
Teenage Mutant Ninja Turtles (Warner Bros – 2006)
teenage_ninja
Kung Fu Panda (Dreamworks – 2008): title says it all
kung_fu_panda

And what else can we expect for in the near future (but no known imitators yet):
Bee movie (Dreamworks – Fall 2007): bee sues humans
Horton Hears a Who (Blue Sky – 2008): elephant and mini-people – based a Dr Seuss story
Everyone’s Hero (Fox – 2007): baseball

(inspired by blog.macgeneration.com)