Ben 10

Ben 10 is an American media franchise created by "Man of Action" (a group consisting of Duncan Rouleau, Joe Casey, Joe Kelly, and Steven T. Seagle) and produced by Cartoon Network Studios.
The franchise is about a boy who acquires a watch-like alien device, called the Omnitrix, that allows him to turn into alien creatures.

Alien Force

Five years after the original series, Ben has apparently taken off the Omnitrix, but, when his Grandpa Max goes missing, he puts it back on, which reboots it and gives Ben a new set of ten aliens (Swampfire, Echo Echo, Humungasaur, Jetray, Big Chill, Spidermonkey, Goop, Brainstorm, Chromastone, and Alien X). Ben's old enemy, Kevin 11, had somehow escaped the Null Void, but has now become (mostly) reformed and joins Ben's team.

Ultimate Alien

Several weeks after the end of Alien Force, Ben now has the Ultimate Omnimatrix/Ultimate Omnitrix/Ultimatrix, which allows him to 'evolve' his aliens into more powerful forms. Even though it was advertised that Ben now has all of his old forms, this doesn't really happen until Ben 10,000 Returns. After Ben gets home to his family, he also has many new "aliens" that he has to try and fight evil with.