Part Time Santa is the fifth stage in Jingle Cat Bell.
Doges, Snaches, and Those Guys will be spawned infinitely at the beginning. Once the base is damaged, Dark Emperor Santa will be spawned, with Kang Roo and Dark Doge. The peons at the start appear at a more rapid rate now.
Dark Emperor Santa has half the health of Dark Emperor Nyandam, but it will almost certainly perma-freeze your cats. Li'l Eraser Cat and Wrestling Cat will both be helpful as they are immune to freeze.
For normal strategy, stall until full wallet, and then when base hit, kill the kangaroos and dark doges asap. When its done, you can time in you speedy units such as Lion Cat, Crazed Cow Cat, and such to chip it down. Or time in your Cats in a Box or you could stack pirate cats, tine then right. And put them in to perma-knockback the Nyandam, a bit hard.
Note that Awakened Bahamut Cat will OHKO the Nyandam, so time it well.