Theories from across the Internet:
1: A wacky Green Lantern used for comic relief.
2: An brave Green Lantern who befriends Hal and is killed off for dramatic effect.
This is the only thing that makes sense. There is no history on who was Abin Sur's partner in sector 2813 (although there were many Earth GL's before Hal Jordan). The closest character to that would be Starkadr, who recruited Abin Sur after he was mortally wounded in battle.3: Abin Sur's partner who's also killed off by Legion.
There are a good number of those too (namely Sinestro), but that is another possibility.4: An traitor Green Lantern who doublecrosses the Corps.
No GL had a partner before 2000.
Perhaps, Abin Sur's 2814 partner? He could serve as a GOOD influence/mentor to Sinestro's BAD one. It makes sense that for time constraint reasons they'll address IMMEDIATELY the fact that each sector has two Lanterns.
Movies have to tell stories differently from comics. In the movie after Sinestro goes bad, they're gonna need someone for Hal to talk to in the corps... They can't just leave him high and dry.
Nevermind. Just read dnno1's post.
or guy since he was due to have a cameo in the earlier drafts.
"John Stewart. Welcome to the Green Lantern Corps."
DUN!! Shock cut to black.