Throughout the Ben 10 franchise, various changes in the continuity, otherwise known as retcons, have been made. Below are most of the retcons made in the franchise.
According to Matt Wayne, they take what they want and ignore what they don't like.
Ben 10: Alien Force
The Plumbers are now an intergalactic police force, when it was established in the original series that they were a secret government organisation comprised of humans only, and several with a racist attitude towards aliens.