Hokum was a hipster pet shop owner, running a store called Rare Pets & Supplies. He had ordered a massive shipment of rabbits in an effort to get rich, but they were failing to sell, even going as far as to put fake horns on one to sell it as a "rare three-horned jackalope from the farthest corners of the Adirondacks".
Outside, Harvey witnessed Muninn and Huginn open a portal to the Hidden City. There, he ran into Baron Draxum, who tasked him with capturing "four unusual pets" and mutated him into an anthropomorphic rabbit with one of his Oozesquitoes.
Michelangelo, while peeking out of the sewer, saw Hokum's rampage across New York City and dubbed him "Man-Bun". The Turtles and April fought Man-Bun, and they were only able to fell him with "Chaos-jitsu" - attacking everything so that at least one of them was guaranteed a hit.
While the Turtles and April were distracted by Baron Draxum, Man-Bun fled, and ran into a mysterious character identifying him or herself as "worse" than Draxum.