Roy is a complete one joke character. He’s a parody of Scrappy Doo and the like, characters injected into an established show in an attempt to freshen things up and skewer towards a younger audience. He’s a product of the radical ‘90s; by the end of the half hour he’ll go off to live with two sexy ladies, and that’ll be that.
As such, he’s essentially a nonentity in the episode “Itchy And Scratchy And Poochie”, and his blandness is all part of the gag. He suddenly appears in the Simpson household, a cool college kid in backwards cap and shades whose presence no one questions.
As well as a counterpoint to Poochie, the hip new canine addition to Itchy And Scratchy, Roy was a response to a real life network note from a Fox executive who felt it was time the show mixed things up a bit with a new member of the Simpson clan.
Roy’s appearance, and everyone’s acceptance of it, is hilarious, but the daftness of this new edgy character suddenly materialising in a beloved show is the most creative way to dismiss a frankly terrible idea from the network suits.