Having tried flying too close to the sun fried his brain. Leaving him batty but lovable. Despite being a gentle kid, Icarus is easy to anger and driven to great acts of spite when especially provoked particularly when consumed by jealousy. When jealous of his father, Daedalus, whom he usually refers to as 'Dad-alus', getting remarried as he was concerned his new spouse would divert his father's attention away from him, he stole Pandora's Box and set the viruses to attack the wedding. Then jealous of Cassandra's new boyfriend Melampus (who resembled him), he snuck into Cupid's cherub-arrow making factory and made an hate arrow. He sung while doing so.
In the clip episode Hercules and the Yearbook, Phil tells that after graduation, Icarus went into manufacturing with his father, Daedelus, and became very wealthy, earning the name "Icarus: The Wax-Wing King".