247=Xmas Bilsy Boss (in End Bosses) doesn't work.
251=Addon DOG (in Enemies) is the Xmas Bilsy Boss.
252=Addon Sparks (in Enemies) is the cat.
253=EMPTY so it isn't listed.

So, change your JCS.ini and make it this way:

253 to 247;
247 to 251;
251 to 252;
252 to 253.

Dont forget the extra data!