update: I was originally focusing on wolf thumbnails because that's what I can see weird on my end, but some of the screenshots by users below show there something going on with image rendering and resizing as a whole, and also that's not consistent across users-I see NPCs as mostly smooth and fine but some people are getting very pixelated images. It feels like there is something really off in the resizing method on certain browsers/devices/etc
Whatever resizing is being done for the thumbnails causes certain wolves to have bleed, you can notice if you turn on darkmode and click around for random wolves.