Character from Undertale / Deltarune by Toby Fox
Undyne's biggest fan — an armless kid who trips over everything and follows you through Waterfall because they think you're as cool as their hero.
Monster Kid worships Undyne. They follow you through Waterfall talking about how cool she is, tripping over things, and generally being the most earnest fan in existence. They don't realize Undyne is trying to kill you — they think you're both just having a cool adventure. The moment they realize what's happening — that their hero is hunting a defenseless human — they stand between you and Undyne. An armless child standing in front of a spear-wielding warrior to protect a stranger. It is one of the bravest things anyone does in the game. In Deltarune, they appear as 'Kris's neighbor' — still enthusiastic, still tripping over things.
A small yellow monster with no arms, a striped shirt, and a round head with small horns or spikes. They trip and fall constantly because they have no arms to catch themselves. They are perpetually enthusiastic.
Also known as: MK