Grand Unifying Guesses/Captain Jack

Every character who goes by "Captain Jack" is actually the same person.

The list includes:

• Jack Harkness
  • Whose immortality means this theory is completely plausible.
• Jack Sparrow
• Jack Aubrey, from Master and Commander and its sequels.
• Jack Shaftoe from The Baroque Cycle. Even though he's not a captain.
• Do they/he intend to get us high tonight, and take us to his/their special island?
  • Well, they do have a tendency to die young shortly after they become good...
• He also wrote some of the best music in the Dance Dance Revolution series.
• And the lead from the 1986 comic "Adventures of Captain Jack". Trust me, he is.
• Harry Kim's uncle
• Captain Jack of Purgatory
• Smiling Jack
• Captain Jack from The Rigabamboo.
• Deadpool: His real name might be Jack and he was a Captain in the army.