Mostly normal show, except for one character who's completely off the rails
Reese from Malcolm in the Middle:
While most Malcolm in the Middle episodes are fairly grounded sitcom plotlines, Reese, the most impulsive and arguably least intelligent member of the family, will wind up doing things like enlisting in the Iraq war as a teenager or attempting to mail himself to China in a crate to beat up his pen pal
Cosmo Kramer from Seinfeld:
While Seinfeld isn't the most grounded show, the main plotline of an episode usually centres around a relatable situation which escalates to farcical extremes. Kramer, on the other hand, through a combination of high charisma and low common sense, will end up doing things like poaching lobsters from ocean traps, becoming the face of a tobacco advertising campaign, getting fired as a mall santa for preaching communism to children, or getting dropped in the ocean and left for dead by the mob