Having not seen the cited episode, I'm not sure if the "bubble boy" turned nasty because of his illness or if he was that way to start with...more context is needed.
Series/Seinfeld: In "The Bubble Boy", George Costanza goes to visit a young man who, due to a rare immune disorder, is confined to a plastic bubble. Said Bubble Boy is nasty, demanding, foul-mouthed, and aggressive.
Having not seen the cited episode, I'm not sure if the "bubble boy" turned nasty because of his illness or if he was that way to start with...more context is needed.