To some of those who know he, Delusional Desire is actually Dark Will/Numbuh 333 from Codename: Kids Next Door (KND) World. I reuse my old KND OC to give him purpose to go on. He’s actually a piece of Numbuh 333, his dark conscious, a voice in his voice, split personality, his personal demon. He somehow split himself from Numbuh 333 and escaped to the Equestria Girls World to be free from scrutiny of his post-decommissioned.
Like any living being that enters another dimension became that form of those indigenous beings. In Equestria Girls World, Dark Will/Numbuh 333 or Delusional Desires is now pure normal Human being but he have magical items from his homeworld to allow him to use his monster powers.
Delusional Desires enroll in Canterlot High and meet Sunset Shimmer after the event of the Fall Formal Dance, there he knew something special about her, that she is not part of this world and have in common with her. Delusional Desire befriend Sunset Shimmer and later become closer than friends.
Delusional Desires is actually a Shadow Monster who can control own shadow as his extension of his limbs and even turn himself into a shadow to move in tight places. He was ‘born’ when Numbuh 333 was contaminated by the Sands of Time and his personality splits.My Little Pony: Friendship is Magic (c) and