[quote=@Hostile]
[@Aether Spawn] [url=https://www.youtube.com/watch?v=sRTUReLBWHA]GOTTA GO FAST[/url]

[@Lmpkio] I believe that all of [i]Doom's[/i] protagonists are actually separate entities, except the one in the first two games. 
[/quote]

There may be "3" different characters actually.

The 1st comes from the original 2 Doom games, yes, but some assumptions say that its also synomomous with Final Doom and Doom 64 (even though they're mostly "remastered copies for the N64 and Playstation games, but do have some evidence of story continuity with the first 2. Do not quote me on this).

The 2nd is from Doom 3.

And yes, the third is from current DOOM, who according to speculation, may well be the ORIGINAL Doomguy himself if it becomes true.

There's also a 4th unofficial character for some Doom RPG that I think serves as an advertisement for Doom 3, who's name could be B.J. Blazkowicz (yes, the same/similar one from Wolfenstein). Appearantly, the website for Doom RPG does state that the player in Doom RPG is the same character from Doom, Doom II, and Doom 3, but is unclear, with some speculation even seeing 3 as a prequel to the first 2 games.

Again, we just have no fuckin' idea if the Doom Slayer is actually separate in AUs or actually one person traveling through space in time. It's confusing IK, I'm just using the official DOOM wiki at this point.