In the episode, April was called by the Turtles after Bebop and Rocksteady crashed the Turtles' sewer lair via Shredder's matter transporter. During April's search for the mutant minions, she finds the matter transporter at Shredder's warehouse and begins taking pictures of the machine. It was at that moment that a stray cat leapt on the control panel and pressed a button that activated the machine, and hopped on the platform next to April. After the activation process ends, April hops off feeling woozy, but quickly notices that her fingernails became claws.
April later returned to her apartment, where her feline transformation continued. She was followed home by a group of stray cats, which irked Irma, who later gave the cats a saucer of milk--which April and the cats drink out of. April's transformation was also affecting her speech, as she meowed and hissed while talking. She later tossed a vase at Vern Fenwick, causing concern from Irma, and it was at that moment that April's physical transformation was completed. April hissed at Irma when she attempted to block her from leaving, and later leapt out the window. She arrived at the warehouse in her quest to reverse her transformation, but she ended up captured by Shredder, who decided to place a mind control collar around her neck.
As a result, April turned heel and became a servant of Shredder, and she left to fulfill Shredder's order to destroy Splinter. The feline villainess went to a zoo and freed a tiger from its cage, and both of them headed to the sewer lair on their mission. Splinter's meditation to overcome his fear of cats is interrupted by the tiger's appearance, and following this, the evil April appeared and hissed at Splinter as she crept closer to him and revealed her mission. Splinter refused to fight April, but the villainess stated that it would not stop her. The Turtles' arrival appeared to break April from the stranglehold, but only temporarily, as she continued her villainous pursuit. Leonardo used his katana swords to destroy the collar, freeing April from Shredder's control. At episode's end, the effects from the transporter wore off, and April was back to her human form.
- As a villainous catwoman, April possessed a feline face, pointed ears, sharp claws, and a tail, while still maintaining her brunette hairstyle and feminine physique. Even in her feline form, April still wore her yellow outfit and white boots.