Mechanikat (voiced by Mark Oliver): The main antagonist of the series, he could be based on Brainiac or Metallo. Mechanikat is a cyborg feline, who constantly plots to conquer Earth. He usually keeps a bit of kryptonite on hand to use against Krypto, or to power up his machines with so they can affect Krypto. He is also a member of the Villains Club. Despite being the main antagonist, he rarely takes matters into his own paws and fight Krypto on his own, normally using machines or other villains to face him, but has (on one occasion) upgraded himself into 'Mega Mechanikat' and lured him to a Kryptonite-covered planet so he could take care of Krypto on his own, but ended up being defeated as well in his final appearance of the series.
Snooky Wookums (voiced by Nicole Bouma): Mechanikat's sidekick and secret agent, Snooky is an evil mastermind kitten who uses his cuteness and smarts to cause all sorts of trouble for Krypto and the Dog Star Patrol. He later became part of the Supercat Fan Club. Snooky is Mechanikat's most trained agent.
Delilah: Another feline agent of Mechanikat. Delilah's outfit changes in season two, adding on purple-colored plates of armor in various areas on her body. She is also in charge of weapons and helped make the Kat-bots and she also knows 9 different types of kung fu.