It's in the episode where Kitty and Dudley saving Christmas. After the cinematic where the T.U.F.F. guys are opening the weapons storage, there will be a Country music sound played. This sound is from the TV serial "Back at the Barnyard"! Some of the... more
In a couple of episodes, you can see a building with a fish bowl over it. That fish bowl is the one used in the series Fairly Odd Parents. Both shows were made by Butch Hartman.