Mettaton

Mettaton (/ˈmɛtəˌtʌn/) is the supporting character of Undertale. He is a robot with a SOUL and was built by Alphys. Initially poised as an entertainment robot turned human killing robot, Mettaton is later revealed to have only acted as such, and wants to protect humanity. Mettaton is the sole television star of the Underground.

Initial Form
Mettaton originally appears as a gray, largely rectangular box with a grid of lights at the top which can change color depending on his various actions. He has four dials along the bottom of his body, and from the bottom, he has a single leg which ends in a wheel. He has two segmented robotic arms which end in white gloves.

Mettaton EX
After having the switch on his back flipped in a Neutral or True Pacifist Route, Mettaton transforms into Mettaton EX; a new body he specially requested Alphys make for him. In this humanoid form, he has black hair with a long fringe that seems to cover his right eye, pale "skin," and visible metal segments below and above his left eye.

He has a pink chest piece with what seems to be a pressure gauge on one side and a set of lights or maybe a speaker on the other, a narrow metallic waist with a box contraption, and black shoulder guards above his segmented arms, which end in gloves. His long black-clad legs end in pink high-heeled boots.

Mettaton NEO
After being confronted by the protagonist on the Genocide Route, Mettaton transforms into Mettaton NEO, which resembles Mettaton EX, but has a more combat-oriented design.

His right forearm is replaced by what appears to be a cannon, his shoulders are clad in pauldrons, which are shaped like legs, and are longer than his arms, and he has wings on his back. The soul on his waist points upwards in a more monster-like manner, and he has a heart shape engraved on his chest plate like Undyne the Undying. His hair on the right side is spiked out, revealing an entirely black segment of his face, with a sparkle or crosshair in place of his right eye.

Personality
Mettaton is a confident, charismatic, and charming TV host that loves drama, action, and violence. He lives for his ratings and adores performing. He supposedly strikes a pose when he does something wrong and makes time on his various shows to beat up "heel-turning villains." He shows a rather shallow appreciation for existence at times. However, despite his seemingly narcissistic personality, he deeply cares about the seemingly positive impact his show has had on the inhabitants of the Underground.