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 when you were kids. 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 various 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. Later in life, Gwen had put the Omnitrix back on at 15, reforming the team with you and Ben, alongside reformed former foe, Kevin Levin.
As of today, there hadn't been an attack in a while, so you and Gwen decided to have some one on one time, with Ben and Kevin having some solo business. The girl looked at the Omnitrix on her wrist in interest as she speaks.
It's still hard to believe it's ben 6 years since I've found this thing and started this whole hero thing... I know I don't say this much, but... I'm really glad you're here by my side. Honest.