Crock Blocked is the twenty second episode of Season 9.
Timmy wishes Mr. Crocker would disappear, but he becomes invisible. Due to this, Dad thinks the house is haunted.
After Mr. Crocker tries finding Timmy's fairies to grind them up to fairy dust, even going to extreme attempts such as hiding in Timmy's toilet, Timmy gets fed up and wishes for Crocker to be gone. Unfortunately, he realizes that he only turned Mr. Crocker invisible. Thinking he found a loophole, Timmy wishes for Crocker to be visible again, only to get his wish rejected since fairies could not do magic on invisible teachers.
Throughout the day, Timmy comes up with several plans to cover his invisible teacher with a substance that would expose him. He first sets up a paint trap for Crocker, placing a bucket of white paint on the door, only to knock the bucket onto himself after Cosmo scared him. Later, Timmy sets up a mud trap with shabby fairy cardboard cut-outs to lure Crocker, only to have Cosmo switch the cut-outs with better ones and cause Timmy to fall in the mud himself.
Finally, Crocker is able to get his hands on Timmy's fairies, but before he can grind them up into magical dust, he is lured to the Turners' kitchen after smelling chicken nuggets there. As he sneaks into Timmy's house, Timmy spills some sticky chicken nugget sauce onto Crocker, revealing him and allowing Cosmo and Wanda to grant Timmy's wish to make Crocker visible again.
Not realizing he has been turned visible again, Crocker walks into the classroom naked the next day, commenting how since he is now invisible, he does not need to bother with getting dressed. Much to his embarrassment, Crocker realizes that everyone could see him, and he runs out in a state of panic, only to get hit by a random train in the hallway.