The Other Darrin: Otis is voiced by Kevin James in the (movie) and by Chris Hardwick in the (series). However, it's subverted with everyone else (most of them voice actors), who got to stay for the series.
Recycled Script: "Free Willy" is very similar to the Jimmy Neutron episode "Monster Hunt". For bonus points, Gene Grillo wrote both episodes, Jim Cummings voices both captains, and Rob Paulsen voices the token nerdy character.
Screwed by the Network: It was moved to Nicktoons Network in 2011, Nick didn't seem to promote much with the show later on.