A bath is something Mr. Kat hates, like most Earth felines (Cats). Yet it is a recurring event for him in several episodes, and also occurs to some other characters.
In Night Of The Zombie Kat, Coop talks Millie into giving a bath in order to get the powder dust off him.
In The Allergy, Burt scrubbing Kat with a brush all part of Coop and Dennis' plan to make him allergic to him
In Dial "B" For Babysitter, Old Lady Munson gives him a Kat after Coop sprays him with a formula of garage.
In Happy Campers, Kat reunited with the family all stinky and covered in poison ivy and Millie ends up giving him a bath.
In Kat Whisperer, Coop get Kat muddy and gives him a bath by whispering into his ear and enjoys it.
In Pet Peeved, A crazy old lady named Harriet gives Kat a bath after seeing him all covered in cat food.