Who is Higgs?

The Unstoppable Higgs has been around the comic for a while but it seems that he's a somebody that the Castle/Otilia recognizes. The question is...who?

The Unstoppable Higgs is really... Bill Heterodyne, Vanished Hero Barry Heterodyne, Hero-in-Hiding Klaus Barry Heterodyne, Zombie Rembrandt Van Rijn, Clankmeister Supreme Andronicus Valois, The Storm King Othar Tryggvassen, Gentleman Adventurer and Transdimensional Traveler! A long-lost Wulfenbach brother Agatha & Gil's son (or descendant) who used a time machine to come back and help None of the above