Inspector Gadget's parents were named Jules and Marie. They bumped into each other in 1957 when Jules was a delivery boy for Alphonse Nozzaire's grocery shop. Dr. Claw's parents were Big Burly Gordon Claw and Marylin (a.k.a. Mom). They also met in 1957, albeit in jail.
Dr Thaw is Dr. Claw's twin brother. They used to be inseparable, until Claw started his criminal empire and Thaw was mysteriously frozen in a gletscher. Unlike his brother and mother, Dr. Thaw wears pink dish washing gloves instead of claws. He has a teenage son called William, who is against being evil and develops a crush on Penny Gadget.
WOMP stands for World Organization of Mega Powers. Its headquarters is inconspicuously located beneath the only skyscraper in town. Despite the size of the organization, Gadget is the only active agent.
Brain is revealed in one episode to have retired from crime fighting as he could no longer work with Gadget as a partner. He has taken up fishing and wearing dungarees. Chief Quimby now has gray hair and has been promoted to be WOMP's chief General's top informant.
We occasionaly get a glimps of what Dr Claw really looks like: very muscular, a bucket shaped head with glowing yellow eyes like the M.A.D. symbol and wearing two golden claws. He sucks his thumbs when he is sleeping.