The Red Heterodyne lived approximately a hundred years prior to the current day. At some time, The Red Heterodyne was engaged in a feud/war with the Unseen Empire, a subterranean kingdom of mutants/constructs, led by another mad Spark with a penchant for lava cannons.
The Red Heterodyne apparently triumphed over the Unseen Emperor, or at least survived the conflict, but(apparently a year longer than necessary), when he developed a taste for bat sandwiches. "Red Heterodyne" now appears to be for bat sandwiches, at least in Mechanicsburg.
Da Boyz fought with him in that campaign, and affectionately recall him as "dot nut."
The Novel Edit
According to a footnote in Agatha H. and the Voice of the Castle, he was the brother of The Black Heterodyne, and the two of them engaged in.. vigorous.. philosophical disputes. One of these intellectual conflicts led to his creating the Spiderroaches which infest Castle Heterodyne.