In one scene, Crocker is sitting in a locker, about to press the button to go to the Crocker Cave, when Principal Waxelplax walks up and sees him. They look at each other for a few seconds, and Crocker screams "FAIRIES!"
Like most everyone else in Dimmsdale, Mr. Crocker believes Jimmy Neutron to be Timmy Turner in some ridiculous big head disguise. When analyzing details to conclude that it's proof Timmy has fairy godparents, his list includes Sanjay claiming to be Yogi Bear in spite of its complete irrelevance.
The Jimmy Timmy Power Hour 2: When Nerds Collide
The entire "Breaking Da Rulez" scene in When Nerds Collide is one long sequence of these. First, Carl falls in love with a turkey, then Cosmo uses magic to constantly beat Sheen at Rock-Paper-Sissors while both of them go to Broken Record levels to remind Jorgen that he's using magic to do this, and finally, Jimmy wishes for Timmy to be dead, leading to him "dying" in a ridiculously hammy fashion and Cindy wailing over him in equally hammy grief. Jorgen's increasingly infuriated reactions make it better.
"I'm riding a hot dog over you! All these pork byproducts have got me feeling blue!"
Dr. Calamitous makes Jorgen eat a sandwich made with rye bread against his wishes. After eating the sandwich, Jorgen comments that it has good mustard.
Sheen wishing to be best friends with Morgan Freeman.
The Jimmy Timmy Power Hour 3: The Jerkinators
When Jimmy and Timmy are creating the villain, Timmy says they should give him a moustache because "moustaches are evil". Cosmo tells Timmy that not everyone who has a moustache is evil. Wanda says "Your mother has a moustache", which causes Cosmo to relent.
One hilarious moment, if painful for Timmy and Jimmy, was when Jimmy gives their creation the name "Shirley" and assures him that it's a cool name. When "Shirley states "Beware the wrath of SHIRLEY", Timmy, not known for having very much self-control anyway, bursts out laughing saying "That's the dumbest name ever." Shirley angrily says to Jimmy "You gave me the dumbest name ever?". The look on Jimmy's face is PRICELESS!
After Jimmy loses his genius, Timmy and Jimmy end up using useless inventions from Jimmy's lab. Timmy yells reactively "Cosmo, you idiot" before apologizing due to habit and correcting "Jimmy, you idiot."