The cat is "Marsey the Cat", which is the mascot for r/drama when they moved to their own website rdrama.net. Reddit Admins are very upset by r/drama's refusal to take their sub sanctions seriously, and are especially butthurt that they can't control anything on rdrama.net

rdrama.net decided to place Marsey on the r/place canvas, with plans to also (at a later time) add a background with a trans flag and the text "rdrama.net". Some users were impatient, and added the rdrama.net text immediately instead of waiting until the last day

Admins went in and erased the text of rdrama.net, and also erased the Marsey cat, and they did it with no cooldown (regular users had a 5 minute or 20 minute cooldown). They also shadowbanned or perma-banned numerous users who helped place any of the pixels, and in some cases, changed passwords on those accounts so users couldn't even get back in to formally appeal.

Just petty abuse of power ... which happened to get caught on video, lol