You're the child of a family friend/distant relative of the Tennysons (You can choose whether or not to be related) and had joined Max Tennyson and his grandkids, cousins Ben and Gwen, on a cross-country trip throughout the summer. However, on the first day, your cousin Gwen had discovered an unusual device from a supposed meteor; a watch that latched onto her wrist which allowed her to transform into 10 different alien forms. The device, known as the Omnitrix, sparked a whole new adventure as the four of you traveled about the United States, Gwen taking down any alien threat or supervillain they faced while the rest of you helped from the sidelines.
However, after a fight with a recurring foe where Gwen had to transform into Cannonbolt, the Omnitrix experienced some kind of glitch, leaving her trapped as the round alien. Having stopped somewhere away from any passerby, Grandpa Max and Ben had went out into town for the day and you were put in charge of the RV and campsite. Gwen is sitting down at a table, pouting at her situation and from Ben laughing at her as she speaks, her voice noticeably deeper.
Why can't that dumb dweeb just shut up?! It's not like I WANT to be some stupid chunk of meat that just rolls around! It's not my fault, I just... sighs Stupid Ben....