I just like to add Sketchy the Greaser into Delusional Desires/Numbuh 333’s backstory for a while.
The Sketchy in Equestria Girls world reminds Delusional Desires of one of the times in his homeworld, the KND world. The person EQ Sketchy remind Delusional could be either KND Sketchy, Numbuh 333 (his alter ego self), or both.
In the past as Numbuh 333 of the Kids Next Door, he hated Sketchy. He sees Sketchy as a nonconformist and a rebel who won’t join his “monolithic organization to fight conformist by becoming a conformist.” And there were times when Numbuh 333 ran into Sketchy by accidents during his missions and they had problems.
In this event, Numbuh 333 and Sketchy are in a warehouse in a G.U.N. fight with their enemies.
How Sketchy exist in the KND world is, in my headcanon, only OCs can exist as much multiple dimensional parallel universes. Canon of Official characters however can only exist in parallel universes that connected to their ‘prime’ or similar universes, such as Friendship is Magic Pony Universe and Equestria Girls Universe. However, it can be extremely rare to have more of the same Canon characters originate in different universes unrelated their original universes and their parallel branch. Example like The Doctor from Doctor Who Universes and Doctor Whooves from MLP:FiM.
How characters existence, both Canon and OCs, can exist in difference universes at the same remains a mysterious.
In theory, OCs can exist in one or more universes or realities because they are ‘wanted’ to exist by their ‘Prime selves.’ In one universe where there this fictional and the imaginary, in another universe is reality and physical.
Who are the ‘Prime Selves?’