Frumpkin came into Caleb's life when Caleb was around twelve-years-old. He was accidentally summoned when Caleb was sketching in his notebook while wishing for a friend. He's been around ever since and the two are inseparable.
Though four-years-old, Frumpkin looks exactly the same as the day Caleb summoned him. In addition to being able to follow complex commands, Frumpkin can be summoned from/sent to a pocket dimension. Caleb can also transfer his senses to Frumpkin, though this renders Caleb's body temporarily blind and deaf.