Bugs Bunny- When Elvis Presley says "Did somebody knock?". Is a reference to the Looney Tunes episode "Rabbit Fire" wherein Bugs Bunny says the same words after coming out from the hole.
When Mr. Turner lands his car in Adrenaland, it's parked in the center of the amusement park. At the end of the episode, the car's parked in the parking lot.
Cosmo and Wanda turn Timmy into sixteen year old Gah in the middle of the park earlier with no problem, but when he wants to be wished back, Cosmo and Wanda say they can't use their magic because they're in public. This may be because there was nobody around/paying attention to Timmy earlier, though.
Timmy was still able to wish away his Gah-look even though Vicky fell in love with him.
Characters saying "that's the password" and dropping somebody down a trapdoor.
When Gah saying "help" while Vicky thinks it means "I love you" in Norwegian.