It's currently unknown how Francisco became a D.O.O.M. agent, but from his accent and according to Butch Hartman, he's from Chicago.
Francisco is a sinister D.O.O.M. agent who usually bears a snarly grin on his face, and is often quick to pull the trigger on his blaster. He seems to have a bit of a dark side to his personality, as seen in Forget Me Mutt, when Snaptrap asked for ideas on how to defeat T.U.F.F., he suggested that they eat them, to which Snaptrap said that that was just "dark and disturbing." This is likely because he is an alligator, which are known for being vicious and eating many different animals. He has been shown to be more intelligent than Snaptrap when it comes to evil plans, as it was his idea to use Snaptrap's invisibility helmet to release all the villains from prison, while Snaptrap just wanted to have fun with it by committing silly crimes.
Despite Francisco's rather intimidating appearance, he is actually a very laid back person and doesn't usually say much. While Ollie and Larry are not usually as evil as he is, Francisco does have a good side, as he cares about Snaptrap, even though he laughed about him a few times. He even apologized for eating Snaptrap's pet hamster (it is unknown if he was hungry, or did it for another reason). Despite Francisco being one of the more evil characters in the series, he enjoys doing things with his fellow D.O.O.M. agents, whether they are committing various crimes in Petropolis, or just hanging out for fun, such as playing games and eating ice cream.
Relationships with other Characters
Francisco seems to have a good friendship with Snaptrap, though Snaptrap gets a little sarcastic towards him at times. Francisco has also laughed at him from time to time. In Snap Dad, it is mentioned that when Snaptrap lost his pet hamster, Francisco apologized for eating it. He also mentioned that Francisco and Ollie are like family to him. Additionally, Francisco has implied that they both share bunk beds when they are in prison.
Francisco seems to have a good friendship with Ollie, but it isn't usually shown. They tend to make a good team when they are paired up and always appear to get along with each other.
Francisco seems to have a good friendship with Larry and is loyal to him (such as in Doom and Gloom). However, before joining his G.L.O.O.M. agency, Francisco and Ollie were willing to throw sticks and stones at him under Snaptrap's order. They both appeared to get along with Larry after they joined him, though.
Francisco was nicer to Keswick than any of the T.U.F.F. agents in Snapnapped, but they still seem to hate each other afterwards.
Dudley, Kitty, and The Chief
He seems to have a hatred for all of them more than Keswick.