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Justin Kirk, Animal Practice
Previous Greatness: He received an Emmy nomination for his part in Angels in America, but he's best known as the lovable and randy fool Andy Botwin on Weeds.
Sadly, the writing on Animal Practice never gave the humans stars credit for being able to act. Instead, their furry, scaled or feathered co-stars got the bulk of the laughs (damn you, Crystal the monkey!), leaving the hominid actors to play second banana.