Mr. Nesmith is a brilliant American chimp who has no choice but to take Sheen seriously and help him find his way on Planet Zeenu. After all, Sheen's ship is the first shot he's had at getting home in 50 years! Mr. Nesmith is a master of all things intellectual -- math, science, sudoku, you name it -- who has been camped out on Planet Zeenu since his rocket crashed there back in the '60s. Though he may not be the world's most tolerant monkey when it comes to Sheen's antics, Nesmith's rocket fixing skills make him one of our hero's only tickets back to Earth.
Sheen crash lands Jimmy Neutron's 'borrowed' rocket on Zeenu, has tons of misguided adventures and deals with the planet's weird creatures and a stranded NASA-trained, talking chimp who joins Sheen on the quest to get home.