Neutral Stupid

A character in Dungeons & Dragons of the "True Neutral" alignment, played poorly due to a fundamental misunderstanding of what "True Neutral" means.
A Neutral Stupid character is borderline obsessed with maintaining the "balance of the world" and will unpredictably switch sides if they believe that the "good guys" are too strong, sometimes in the middle of combat.

(See also: Lawful Stupid, Chaotic Stupid)

Ranger: "I shoot the orc in the middle with my bow, dealing 16 piercing damage."

Neutral Stupid Druid: "Oh, uh, I heal the orc!"

Ranger: "You WHAT?"

NSD: "My character believes that you guys are killing the orcs too quickly."

DM: "There's literally three orcs on you right now, buddy."