Leo is 9 and is very similar to his sister Rebecca: just like her, he loves adventure, but he'd prefer it was on videogames and television! Running around Fogville haunting for mysteries is not for him: why would you waste energies and struggle when you could live incredible adventures right by your extremely comfortable couch, perhaps even snacking on some delicious fried chips? 
Leo's laziness is contagious, especially to Pat Bat... but in times of need, laziness is out of the question: when it's a matter of helping creatures in trouble, Leo is the first one to step up with some crazy new invention!