Image credit EPPH (Every Painter Paints Himself), here. Rembrandt van Rijn, 1654, etched copper printing plate, size unspecified, held by V+A Museum, Amsterdam.
Analysis from Wikipedia:
This print shows a homely scene of maternal affection but it is also a powerful piece of Christian symbolism. While the cat on the left is playing with the Virgin's hem, a snake can be seen slithering out from under her skirt. The Virgin is treading on the snake, symbolising her role as the new Eve, who will triumph over original sin. Joseph looks in from outside the window, symbolising his closeness to, but also his separation from, the Virgin and Child. The pattern of the window's glazing creates the impression of a halo around the Virgin's head.
My take? The kitty is over there on the left edge, in relative obscurity, doing what cats do (playing). Oblivious to all the religious symbolism swirling around it, Rembrandt's cat just is.