Fenwick P. "Fen" Tennyson lives in an alternate Bellwood, where the Plumbers run a school for young super heroes. Fen is Gwen's twin brother, and is a star pupil at the school. Although, since his Grandpa is Earth's Magister, he thinks he can skip classes whenever he likes.
Fen's ability allows him to literally see when things don't belong. While it's not the most spectacular super power, it helps him spot dimensional trespassers.
Fen got this power, not from his Anodite grandmother, but from an accident, in his scientist father's lab. Being twins, Fen is very close to Gwen, but never supported her relationship with Kevin. Thus, when his father told him Gwen had taken a boy named Ryan to a school function, Fen was relieved,
Fen's reasons for skipping classes usually relate to the amenities offered at the school. For an educational facility, it has one floor for entertainment, and another floor with stores, like a mall. The most unusual thing in the school are the elevators. Once you pass a floor, the button for it vanishes, and you cant access it again until the elevator reaches either the lowest or upper most level.