A person who is considered to be crazy; who does things which aren't generally accepted or which are out-of-character.

when your girlfriend tries to put her hand on your chest and you then flick your fingers signaling her to go higher to your head so you can whisper in her ear to succ it.

Fat Thor holding a hammer and an axe trying to kill papa Thanos with a rock collection and forgot about bringing Ant Man to fight Thanos.

Also found in Death Note where Saitama got sniped by Goku just because he forgot to go for the Ant Man on Goku's head.