Chell

Chell was an individual who often carried a Portal Gun.

Biography
She was present near the Twelfth Doctor when a child scanned Scooby-Doo and the Mystery Monster onto a toy pad. She had since been moved onto the pad when the room dissolved and revealed them to be in the Land of Oz. (NOTVALID: Endless Awesome)

She was later walking through the Brick Boulevard without her Portal Gun when the Twelfth Doctor, Peter Venkman, and Doc Brown, crashed their vehicles into each other. (NOTVALID: Doctor, Doctor, Doctor)

Behind the scenes
Chell is the main protagonist in the Portal franchise.