Dexter_s Laboratory ｜ Santa Who？ ｜ Cartoon Network

Dexter tries to prove to Dee Dee that Santa Claus is not real and is in fact their father in disguise. Past the vaulted doors lives the smartest boy the world has ever seen, Dexter, boy genius! He's constantly creating dazzling, world-saving inventions in his secret laboratory. His big sister Dee Dee frequently wrecks his experiments. However, he has bigger problems such as his nemesis, Mandark, his brilliant rival at Huber Elementary School. Mom and Dad, of course, have no idea what their little angel is up to.