Despite suspicions that "Clu" is actually short for "Clueless", Clu Bell isn't quite as dingy as he first appears to be. (And actually it's short for "Cluett".) At a year or two older than Jack, Clu is the oldest of the show's three main children in the first season. He's a pal of Jack's, but can generally sway to Fi's point of view when it concerns the supernatural. He's not the sharpest stick in the woods, but he's a good friend to both Jack and Fi. He sides naturally with Jack when it comes to tormenting Fi, but is quite happy setting gremlin traps and jumping into quantum singularities with Fiona. He's seen more of the supernatural than Jack has so he more easily believes Fi's theories on the weirdness that they encounter.Being a little brother himself, he's also a little more understanding of Fiona's frustrations with Jack sometimes. Clu thinks that his own big brother Carey is "the coolest" and tries to help Jack see things from Fi's perspective.
He is accepted into the University of California, Santa Cruz early in the second season. It's a school he chose because it had good surfing. It doesn't take him long to settle in there. By the time he calls Jack in "Werewolf" he has already counted 63 girls in his new dormitory.
By the third season Clu has settled into college and a major: philosophy. He puts in an appearance in the first several episodes of the season and it's clear that his open-minded attitute toward the inexplicable is completely intact. He supports Annie's more unusual suppositions as readily as he supported Fi.