A.J.'s TV has something called a Parental Block, which prevents him from watching any non-educational programs (as well as any animal violence on the educational programs).
This episode marks the first appearance of Chester's mother, yet she was only seen in a photo picture.
When Timmy is trying to fake a dog attack, he doesn't realize that Cosmo and Wanda accidentally left and were replaced with real junkyard dogs. He doesn't realize this until he's actually attacked, despite the real junkyard dogs obviously being a different color than Cosmo and Wanda.
This gag is repeated in Spring Break-Up, an episode with a slightly similar premise.
Cosmo's footprints are gone from Timmy's face when he notes that Chester and A.J. were coming.
The serpentines that Chester throws to A.J. are gone a scene after he throws them.
When Cosmo initially barks at Jimmy when in his dog form, his barking sounds similar to a real dog. Later when he's trying to get Jimmy to come back and he barks again, he simply says "Bark bark" in his normal voice.
When Jimmy was seen at the end of the episode, Cosmo's shadow turns red for an extremely short second.
Cosmo: Ooh, look, a cute little bee. I'm going to name you Cindy.
Cindy the Bee: [flies off and then gets eaten by a bird]
Cosmo: Cindy!!! NOOOOOOOO! (sobs) It's too SOOOOOONNN!