|Joey "The Rat" Epstein|
"That's a good one, Harley! That's a great one! I'll be laughing at that one for years and years. I'll probably tell my grandkids about it sixty years from now. Unless of course if I don't have grandkids, and then I'll tell some strange kids in the park. And the cops will come and say, 'You in the raincoat...'"
- — Joey
He and Frankie are best friends and are often seen together, often torturing little kids along Frankie's side even after Harley is gone. Though he never fully befriends Cory and Shawn like Frankie did, Joey eventually stops bullying them and the three become good associates.
After Harley leaves, Frankie and Joey attempt working as lackeys for Eric Matthews, but they ultimately wind up working for the new guy, Griffin Hawkins, in Pop Quiz. After Griff's last appearance, Frankie and Joey start working independently.
In The Thrilla' in the Phila', he is the only student applying to the John Adams High wrestling team in Cory's weight class. After training with Frankie who only knows Sumo wrestling, Cory quickly beats him, but he cries fix and challenges Cory to a rematch for bragging rights. The fight escalates beyond a simple wrestling match, and there is really no discernable outcome.In City Slackers, Joey challenged Eric to a game of pool, claiming he is an expert pool shot. The match doesn't end, and he and Eric are equally bad. Until Graduation, this is his last appearance.
Even though he doesn't appear in the episode, Joey is responsible for dressing Cory and Shawn up like cheerleaders. Unlike Frankie, he is suspended for his deed. Mr. Feeny suggests that Frankie find friends that are a better influence, and Frankie befriends Cory and Shawn.
In Graduation, though, he appears again (this time with short hair). He seems to have reconnected with Frankie, and has returned to his criminal ways. Even though he considers Cory and Shawn his friends, he wants them to write down their addresses so he can go to their houses and rob them.
In the episode Girl Meets Flaws (from the first season of Girl Meets World), there is an award named after him called the "Joseph T.R Epstein Confidence Award", the T.R standing for "The Rat". It is awarded to Farkle, son of Stuart Minkus, whose last appearance in Boy Meets World is also Graduation, just like Joey's.