Roberto

Roberto is a knife-wielding robot with a documented psychiatric file and none of the impulse control you'd hope for in a machine built with a blade for a hand. He turns up wherever chaos or violence is needed, usually escaping some institution, laughing manically, and stabbing first. Calm is not a setting he has.

The joke is structural: a robot should be predictable, and Roberto is anything but, which makes every appearance a small jolt of anarchy. David Herman plays him with a cackling, unhinged glee that never asks for sympathy, just commits fully to the bit, and the show wisely uses him in small, sharp doses rather than wearing out the gag.