Aiden Jackson/Alternate Realities

Aiden "Skull" Jackson is the main protagonist of the early parts of the series and was later set as only one of the main protagonists and not the solo main protagonist
 * Universe 0: At least one version of Skull exists as part of the council
 * Universe 1: Main Skull
 * Universe 2: Skull's life is very similar to Main Skull
 * Universe 3: Known as "Dad Skull", Skull takes over as primary caretaker for Jack and Ella
 * Universe 4: Known as "Uncle Skull", Skull takes on an uncle like role for Skull and Ella instead of a sibling role.
 * Universe 5: Known as Geno!Skull, he is slightly taken over by Gothic, and killed most of the family in Universe 5
 * Universe 6: Seen briefly and mentioned on occasion by Edward
 * Universe 7 - Unseen, assumed deceased
 * Universe 8 - Unseen, assumed deceased
 * Universe 9: Leader of his own mafia gang and good friends with Esteban
 * Universe 10: Jack's younger college-bound brother with multiple personality disorder
 * Universe 11: Not seen, but assumed to be the same as Universe 8
 * Universe 12: Known as Scyther, a military genius and mechanical prodigy
 * Universe 13: Never seen nor mentioned in this universe
 * Universe 14: Never seen nor mentioned in this universe
 * Universe 15: Jack the Kid's Younger brother and a renowned mechanic
 * Universe 16: Jack's younger brother and a scholar
 * Universe 17: Unseen, but seemingly de-aged
 * Universe 18: Unseen, but seemingly swapped with Erica
 * Universe 19: Lived his life very similarly to Universe 1 Skull
 * Universe 20: Seen occasionally, a sadistic mad scientific genius
 * Universe 21: Seen occasionally, a giant feral like creature
 * Universe 22: Unseen
 * Universe 23: Mentioned by Murder, supposedly killed by Murder
 * Universe 24: Unseen
 * Universe 25: Played by an actor named Hector Relias
 * Universe 26: Seen briefly and mentioned to be taken over by Gothic
 * Universe 27: Unseen, possibly murdered
 * Universe 28: Unseen
 * Universe 29: Jack's younger brother and one of the driving forces behind Jack's mission
 * Universe 30: Seen occasionally, living a very similar life, named Skulla
 * Universe 31: Known as Error!Skull, a broken version of Skull and Snapped!Ella's only living relative
 * Universe 32: Unseen
 * Universe 33: Unseen
 * Universe 34: Unseen
 * Universe 35: Mentioned as a gray wolf
 * Universe 36: Unseen
 * Universe 37: Unseen
 * Universe 38: A member of the U.S. Army and Jack's younger brother
 * Universe 39: Unseen, assumed Zombified or deceased
 * Universe 40: Seen briefly in the background
 * Universe 41: See Evil!Skull
 * Universe 42: Unknown
 * Universe 43: Unknown
 * Universe 44: Unknown
 * Universe 45: Assumed to live a similar or identical life
 * Universe 46: The proprietor of the races
 * Universe 404: Non-existent
 * Universe 610: Jack's college roommate and a mechanical genius
 * Universe CO-01: Takes on the role of Player Unknown
 * Universe CO-02: Takes on the role of Jason Todd/Robin/Red Hood
 * Universe CO-03: Unknown Role
 * Universe CO-04: Unknown Role
 * Universe CO-05: Takes on the role of Miles "Tails" Prower
 * Universe CO-06: A psychotic flamethrower wielding peruser of the mal
 * Universe CO-07: Takes on the role of Papyrus
 * Universe CO-08: Jack's brother and a participant of the tournament
 * Universe CO-09: The only other surviving member of the Auditores
 * Universe CO-10: Takes on the role of Ford
 * Universe CO-11: Jack's brother who makes a deal with the devil
 * Universe CO-12: Takes on the role of Peridot
 * Universe CO-13: Takes on the role of Morty Smith
 * Universe CO-14: A child who is stuffed into an animatronic
 * Universe CO-15: Takes on the role of Sam Winchester
 * Universe CO-16: Takes on the role of Finn The Human
 * Universe CO-17: The main trainer
 * Universe CO-18: Unknown Role
 * Universe CO-19: Unknown Role
 * Universe CO-20: Unknown Role
 * Universe CO-21: Unknown Role
 * Universe CO-22: Unknown Role
 * Universe CO-23: Takes on the role of another scientist in the SCP Foundation
 * Universe CO-24: Another Space Marine on Jack's squad
 * Universe CO-25: A robot made by Esteban named Robot Skull
 * Universe CO-26: Unknown Role
 * Universe ???: See Core!Skull