Origin: Mario is Missing!
Luigi rarely gets first billing in his games, but maybe that's because he's secretly a socially awkward creep.
In Mario is Missing! players take control of the other brother in an educational search around the world for everyone's favourite super plumber. For some reason though, the animators gave him an odd idle stance that has Luigi standing perfectly erect with his bulging eyes staring forward in an unblinking trance.
Naturally, the Internet delighted in putting the creepy face next to all sorts of situations, reflecting their own incredible inner awkwardness.