The Watcher assigned to watch over Earth.
Uatu made his first appearance in Fantastic Four #13 back in 1963 (created by Stan Lee and Jack Kirby, naturally). He’s part of an alien race known as the Watchers, who, after a disastrous attempt at helping a planet called Prosilicus that ended in a genocidal war, vowed to never again to interfere in the affairs of other races.
Watchful observer: Having made that vow, the Watchers decided to spread out across the universe, choose a solar system each, and just, well, watch and observe their chosen turf. Yes, that’s like an entire race of Peeping Toms.
Moon dweller: Uatu is the Watcher assigned to watch over Earth, and he lives on the Blue Area of the Moon, an apparently Earth-like area with water and breathable air.
Creepy presence: He has a tendency to just appear out of nowhere and just stand there, watching. Creepy, yes, but if he’s there, chances are something BIG is going to go down soon.
Mighty powers: As a Watcher, Uatu is immortal, and possesses powerful psionic abilities as well as various other powers, including flight, telepathy, teleportation, superhuman intelligence and so on. In the 1985 edition of the Official Handbook Of The Marvel Universe, Uatu’s power was said to be equal to that of other cosmic beings such as Galactus and Odin.
Oathbreaker: The Watchers’ vow means that even if someone is dying at his feet, Uatu cannot lift a finger to help that person. All the same, Uatu has apparently broken his vow of non-interference more than 400 times before (according to the Dreaming Celestial in Eternals #3 in 2008), and has actually been cast out of his race before because of his transgressions.
A bother to Galactus: In Fantastic Four #48, Uatu once again broke his vow and tried to prevent the Silver Surfer from leading the world-devouring Galactus to the Earth. Then, in 1982’s Fantastic Four #262, the Shi’ar prosecuted Mister Fantastic for saving Galactus’ life, but Uatu stepped in to defend Richards, roping in Odin, Eternity, and even Galactus as witnesses to help the defence.
Family man: In the recently-concluded FF series, the FF visited his home, where they met … his pregnant wife! Where she is at the time of Original Sin is unknown right now, but don’t be surprised if she (and her baby) turn up somewhere along the road! – Michael Cheang