T. J. Slick, along with A.J. Slick, are brothers with a troubled history.
In "The Hall Monitor and the Lunch Lady", while Steve and Klaus investigate the cause of several students becoming ill during lunch, they discover a large amount of sawdust being stored in the kitchen. Working with Hank Turlington who is also investigating, he manages to get Steve sent to the Chimdale Juvenile Detention Center where he manages to make friends with T. J. by catching him in a 'trust fall.'
With a positive endorsement from T. J., A. J. accepts him in the the hall monitors, where he learns that under the direction of Principal Lewis, they've been shaking down students. He also learns that Lewis, looking to expand the need for sawdust generated by his Christmas tree farm, has been poisoning the students and plans on doing the same to the entire town.
When they try to take their evidence to Turlington, they find he has been killed. The hall monitors are invited out to Lewis' Christmas tree farm for the poisoning, but he also reveals that he knows there's a mole. Having taken Turlington's phone, he dials up Steve. Facing capture, Steve uses the power of his leg muscles that he built up while in juvie to leap over the gang and drink the poison himself. Klaus makes a timely arrival with the former lunch ladies and they rout the gang. Steve is saved by a salsbury gravy IV as Klaus informs him that Lewis got away.