Ben 10

Ben 10 is an American animated series created by the group Man of Action and produced by Cartoon Network Studios.Ten-year-old Ben Tennyson, his ten-year-old paternal first-cousin Gwen, and their paternal Grandpa Max start 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. The device attaches permanently to his wrist and gives him the ability to transform into a numerous variety of alien life-forms, each with their own unique powers and abilities. Although Ben realizes that he has a responsibility to help and save others with these new abilities at his disposal, he is not above a little ten-year-old super-powered mischief now and then. Along with Gwen and Max, Ben embarks on an adventure to fight evil, both extraterrestrial and earthly.

Ghostfreaked Out (Season 2, Episode 11)
Ghostfreak escapes from the Omnitrix. Ghostfreak removes his second layer of skin in order to possess Ben, revealing a horrifying creature underneath. As a side effect of removing it, though, he can no longer withstand sunlight and is forced to retreat. Ghostfreak scares the circus trio into working for him as he schemes to possess Ben and gain control of the Omnitrix. He possessed several characters in the process.

Midnight Madness (Season 3, Episode 2)
While visiting a mega-mall, Ben and Gwen watch a hypnotist perform. Gwen volunteers Ben as a test subject, and the host, Sublimino, successfully hypnotizes him. When asked to act like an alien, Ben naturally turns to the Omnitrix and almost changes in front of the audience. Even though he is stopped by Gwen, the trouble doesn't end there. Sublimino is able to use those he hypnotizes to commit crimes in their dream state, and the alien-equipped Ben proves to be the perfect accomplice. Using Ben, Sublimino is able to steal parts to make a much bigger hypnotism device, this time hypnotizing everyone in the mall including Gwen and Grandpa. But Ben escapes the hypno beam. Ben stops him as Wildvine and Sublimino is presumably arrested.

CN Latin America Children's Day Marathon Promo: "Bob the Blob"
In this noncanon promo aired in Latin America, Gwen is in danger of being taken over by an alien lifeform. Ben transforms to come to her aid, only to receive a comically slow blob alien that fails to reach her in time. Gwen retains just enough control to slap him.