The first ever cat to appear on any Blockchain was on the 28/9/2014, over 10 years ago. This cat made using ACSII art and left as a message by the person who mined Block ID 322,917. You can view this using https://messagesfromthemines.brangerbriz.com and navigating to 592/11288 in the archive

The creator of this cat is Satoshi and the cat really wants to know who his owner is.

. /\_/\

___/ o o \

/~___ m)