L-Ron's origins are unknown, as he appears along with Brainiac in the beginning of the movie. He carries out Brainiac's orders throughout the entire movie.
In the final scene, L-Ron finds the remnant of the Brainiac symbol on the ground, after Brainiac was destroyed. He picks up the symbol, and looks directly at the audience, saying "Yeah, I know. But I'm a glutton for punishment."
In the comics, L-Ron (full name L-Ron H*bb*rd) is the robot companion of intergalactic trader Manga Khan. He eventually became a member of the Justice League (mostly working on administration and maintenance).