Gennosuke is first seen in the episode "The Big Brawl, Part 2". He retains his persona as a shady bounty hunter, but unlike in Usagi Yojimbo, he is a heavy gambler, as opposed to being a drunkard in the comics. In the Battle Nexus Tournament he defeats an unknown Clawed combatant in Tier 1, an unknown Octopus Contestant in Tier 2 and receives a free pass to the semifinals, where he loses to Kluh. Notably, Gen irritates the Turtles with his behavior, as well as Casey, who he calls "Saru" (monkey or ape). In the episode "The Christmas Aliens", Gen comes to the Turtles' holiday party. In the episode "Samurai Tourist", inspired by a New York City citizen, Gennosuke dons an outfit nearly identical to Rocksteady's in the 1987 TV series.
Gennosuke appears in "Wedding Bells and Bytes" for Casey and April's wedding. When he realized he had to bring a present for the wedding, he tried to swipe Hisomi-Shisho's present as his own. Hisomi was not amused.
The name "Gennosuke" would be pronounced with a hard G sound and a nearly silent U. His name has never been pronounced correctly on the show; most of the time, his name has been said as if the G in his name would be pronounced with a "J", thus making his nickname sound like "Jen". In "Samurai Tourist", the G was pronounced correctly, but the U in his name was turned into a long U. His nickname is again pronounced like "Jen" by Usagi in "Wedding Bells and Bytes".