Dexter is your typical lab-coat wearing, three-foot-tall science genius with a strange accent. He tries to run his science lab quietly behind a bookshelf in his house, but his biggest challenge is keeping his meddling sister Dee Dee from ruining his great inventions.
Dee Dee is Dexter's big sister, and annoys him constantly while he's trying to make scientific discoveries. She is very girly, and often dances through Dexter's lab breaking important equipment. She might seem silly but she's good at tricking her brother.
Dexter's sworn enemy Mandark is almost as clever as Dexter is, but his lab is even bigger and better. Mandark's main ambition is to shut down Dexter's lab and be the only scientific genius around. He has a crush on Dee Dee, and his real name is actually Susan!
Dexter's happy home-maker mother has no idea her son has a secret working laboratory in their home. Often her demands around the house get in the way of Dexter's work, and she embarrasses him sometimes, but they are still quite close.
Dad is blissfully unaware of Dexter's lab, and Dexter does his part to keep it that way. He usually treats simple competitions between his children as very serious and important - even silly snowball fights - and thinks Dee Dee is better at sports.