The Crocker Cave is Mr. Crocker's secret base in which he researches all fairy-related activity and plans his numerous evil plots to capture Timmy's Fairy Godparents.
The Crocker Cave was originally a Telephone Booth in the Janitor's closet in "Transparents!" where Crocker did nothing but ramble on about his desires for world domination and complain about his fellow teachers, but as he began to find more proof on Fairies, he used school funds for the science lab to build a giant underground lair beneath the school to further his research. The Crocker Cave possesses plenty of equipment to aid Crocker in his research such as a large super-computer, fairy detecting and capturing equipment, a large scale model of Fairy World, containers filled with Fairy DNA such as wings, crowns, and hair, numerous posters that say "I hate Timmy Turner" with throwing darts on pictures of Timmy, a sign with Crocker's picture on it that says The Crocker Cave (briefly changed to a picture of Timmy that says "The Timmy Cave" and "Welcome Cindy!" in "Jimmy Timmy Power Hour 2: When Nerds Collide"), and a large room containing numerous unused evil plots for destroying Timmy and capturing his fairies. In Teacher's Pet, Crocker filled the Crocker Cave with caged animals. He then used his Mother device on himself to turn himself into the ultimate fairy hunting animal with many qualities of the caged animals.
A running gag associated with the Crocker Cave was that whoever fell through the secret tube into the lair would miss the preset mattress and land on floor instead. The preset mattress would then be set in the place they had landed.
In the episode, "Back To The Norm", the Crocker Cave sign says, "WELCOME TO THE CROCKER CAVE. FAIRIES!"