No show in TV history has a bench as deep as The Simpsons’. Over 30 years of broadcasting has given them a whole town’s worth of weird and wonderful characters to play with, and they’ve been eager to add real depth to most of the roster. Springfield residents may debut as stereotypes or quick gags, but in due course they're often given real depth.
Sometimes, though, they bring out a one and done character. They show up, they do their bit, and they leave town, never to be seen again. This may be due to a guest voice who they can’t reasonably bring back, or simply come down to the limitations of the characters - not every creation has to have a fleshed out backstory, a family history and so forth - there just aren’t enough hours in the day.
The brevity of a character’s life span does not necessarily have any bearing on the quality, though. Some of The Simpsons’ most indelible creations stuck around for no longer than the one episode - their runs were as brief as they come, but the jokes and impressions left are as memorable as any the show has had.
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.