Sir George's History
Background
George was born in 231 AD in ancient Rome. He acquired immortality at some point by unknown means, living for over 900 years before becoming a knight in the medieval era.
Sir George forged the seal that kept the Lucubras at bay seventeen centuries ago. He also defeated their master, Dagon, with the sword Ascalon, carving out Dagon's heart and pinning it to the ground with the sword. He is the "First Forever Knight", having founded the Forever Knights.
Ultimate Alien
Sir George moved to the Bellwood Senior Village and lived there for years until the events of The Creature from Beyond. He had a coin with the same symbol as the seal that held the Lucubra. He somehow knew when the seal was destroyed and immediately left. At the end of the episode he was seen looking at the damaged seal, looking down, then leaving.
In Ben 10,000 Returns, Professor Paradox warns Ben to "Beware Old George" and the Creature from Beyond.
In Prisoner Number 775 Is Missing, Sir George arrives at Area 51, where he attacks the guards and removes the base, leaving a crater. A later episode revealed that he turned Area 51 into a Forever Knights stronghold.
In The Purge, Sir George, escorted by two high-tech Forever Knights, appears during a meeting between Enoch, Driscoll, Patrick and Urien. After a brief fight with Driscoll, he is identified as the founder of the Forever Knights and unites the factions into one. Sir George's first order was the Forever Knights target the aliens living on Earth and remove them whatever way possible. He later sends Driscoll to lead the Forever Knight soldiers into attacking an alien air-lift area that Ben was guarding. Upon learning of Driscoll's defeat, Sir George is not disappointed as it was just a distraction for a bigger plan. Sir George has Driscoll lead the Forever Knights while he is away and to have the Forever Knights ready upon his return, "for the battle of 100 lifetimes".
Sir George's trip is explained in A Knight to Remember: he has been on a quest to find Ascalon and Dagon's heart, planning to use his old sword to destroy the heart once and for all. Using a long series of calculations, Sir George found when and where the shrine that holds Ascalon and the heart would appear next, leading a team of Forever Knights to intercept it.
At the shrine, Sir George and his knights were ambushed by Dagon's cult, the Flame Keeper's Circle, and their new leader, Vilgax. Vilgax tossed Sir George aside and grabbed Ascalon, gaining control over the sword's powers in the process. Sir George and Driscoll tried to stop Vilgax from freeing Dagon, and in the process, Vilgax was sucked into Dagon's dimension. Sir George was able to regain Ascalon, and his youth.
Immediately following this, in Solitary Alignment, Azmuth appeared and explained via a holographic flashback that he forged Ascalon and gave it to George in hopes that he could defeat Dagon. Now Azmuth wants Ascalon back, because he fears that Dagon will not underestimate Sir George a second time.
Sir George leaves the area via a rift in space-time created by Ascalon and goes back to Area 51. Using a lock of hair Kevin pulled out, Gwen tracked down Sir George to Area 51 where Ultimate Humungousaur fought him. Ultimate Humungousaur and Sir George made a compromise: if Sir George fights Dagon and loses, he will give Ben the Ascalon.
In The Beginning of the End, Sir George started a war with the Flame Keepers' Circle. Then he goes on challenging Dagon to a battle. Instead, Dagon gives him Vilgax to battle with, but Ben arrives to assist George against the powered-up alien.
In The Ultimate Enemy: Part 2, Sir George takes a direct lightning attack from Dagon and tries to defend himself using Ascalon. However, this backfired since Ascalon merely conducted the lightning into George himself, turning him into an old man once more and electrifying him to the point where he crumbled into dust. Following his death, Ben took Ascalon and used it against Vilgax, mentioning George's catchphrase before charging into battle and defeated his old nemesis.