Ben 10

The show revolves around Ben Tennyson, his cousin Gwen, and their grandfather Max. During the start of their summer camping trip, Ben goes stomping off into the woods after another fight with Gwen, whom he is not happy to have along on the trip, and finds an alien pod on the ground. When he examines it, he finds a mysterious, watch-like device, called the Omnitrix, stored inside. The device attaches permanently to his wrist and gives him the ability to transform into a variety of alien lifeforms, each with their own unique powers, quite similar to DC's Dial H for Hero comic. Although Ben realizes that he has a responsibility to help others with these new abilities at his disposal, he is not above a little superpowered mischief now and then.

Aliens:
Diamondhead
Heatblast
XLR8
Wildmutt
Ghostfreak
Grey Matter
Four Arms
Stinkfly
Ripjaws
Upgrade
Cannonblot
Eye Guy
Wildvine
Ditto
Benmummy
Benviktor
Benwolf
Upchuck
Way Big