Donny was raised in the Shelbyville Orphanage, not knowing who his parents were and unhappy not knowing where his real family is. Donny's most prominent traits are his mischievousness, rebelliousness, disrespect for authority and sharp tongue. Donny was found boxing with a bee hive by Principal Skinner and Superintendent Chalmers at the orphanage when they were looking for a snitch on Bart's plans and they decided to use him as the new snitch.
He was originally Bart's rival, being a better prankster. However, after Bart pranked Skinner in front of the whole school and got in serious trouble, Donny pretended to have done it and was quickly befriended by Bart. He joined Bart's circle of friends, acquiring a stash of Blue Vines from Bart as a token of appreciation. But when most of Bart and Donny's pranks fail, Groundskeeper Willie informs Bart of a "rat" in his circle. Bart suspects that the snitch is Milhouse, because he grew tired of being in Bart's shadow, so Bart's group of friends Milhouse, Nelson and Donny go on a bikeride, where they lock Milhouse up and leave him in a locker in the middle of nowhere.
However, Bart finds out Donny is the snitch when he discovers that Donny gave Skinner some of the Blue Vines that he gave to Donny as a gift. Him and Nelson take him to a storage room, where Bart and Donny have a heartfelt moment before Bart reveals that the room is full of Diet Coke and Mentos, which explode upon impact with one another. However, Skinner, Chalmers, and Willie (who was revealed to be another snitch for Skinner) arrive, forcing Nelson to flee. Bart attempts to flee as well, but is grabbed by Skinner and taken away with the intention of being suspended for a week. But Donny, feeling guilty that he betrayed the only person who cared about him, sets off the Diet Coke and Mentos, engulfing Skinner, Chalmers, and Willie. Donny escapes with Bart onto the rooftop. Donny and Bart agree to stay friends, although Donny has to leave Springfield. He and Bart haven't gotten into contact since, and his current whereabouts are unknown. However, Donny and Bart did talk about hanging out sometime in the future, but it is unknown if that will actually happen.
Behind the Laughter
Donny is based on Joseph D. Pistone aka Donnie Brasco, a real life FBI agent who infiltrated the Mafia in New York City for six years. He was portrayed by Johnny Depp in the film Donnie Brasco. Donny is also based on the character Billy Costigan, played by Leonardo DiCaprio in the 2006 film The Departed, Directed by Martin Scorsese.