In the TMNT Christmas Special, The Christmas Aliens, while enjoying a Christmas Eve on the surface, Michelangelo finds a stray male cat and names him Klunk, and decided to keep him as a pet. Klunk was caught in a Purple Dragon battle, but escaped unharmed with Mikey. Mikey then takes Klunk to live in the lair with him and his family.
When the Foot Mystics used their ninja abilities to plague the five members of the TMNT's minds, they dreamed Klunk drowned when Bishop flooded their lair. Klunk is seen in one episode of BTTS.