This blooper is found in the episode "The Wolf who Cried Boy"
Orson tells Booker and Shelden the story of the Wolf who cried boy (Roy is ringinig the bell and no one cares:) When the Wolf denies the boy the first time his nose is red. 2nd time his nose is black. 3rd time his nose is red.
Only one slip-up for Garfield? Obviously, the show must get lots of complaints of errors in their show. Remember the one where they poke fun at it? It's daytime, the sky's white, Garfield is blue, and an owl says What? Or something like that.