Iago Heterodyne was an ancestor of Agatha's about which little is known beyond the fact that he preferred to conduct his medical experiments in the Castle Heterodyne laboratory nicknamed the "Red Playroom", where he enjoyed working to the screams of his victims, or those supplied by the Playroom's Scream Emulator when the real thing was unavailable.

He shares the Brythonic adaptation of the Greek/Hebrew name Jacob (James is the Latinic derivation of the same name), Iago, with one of the great villains of literature, Iago from Shakespeare's Othello.

Whether Iago Heterodyne was also a malicious master manipulator of men, twisting love into jealousy and trust into murder, is as yet unknown. But it wouldn't be too surprising.