In the episode, 'Halloween,' it was revealed that she is one of the Sugar and Spice 800 cyborgs from the future. They were supposed to be "super sweet and giving and make the world a better place," but something had malfunctioned. Over time, they would become crazier and crazier, until their sweetness turned into evil. Apparently, the cyborgs had a problem of overheating, due to their evilness. They were all then sent to the 21st century.
It was also revealed that the two things that got her mad were "naughty nibblers" and chihuahuas.
Debbie is played by Kay Panabaker, who is the sister of former DCOM stalemate Danielle Panabaker, and currently stars as Daphne Powell in the ABC adventure series "No Ordinary Family."