Cats
Cats are generally loved on 4chan, despite some people posting TortureCat and Zippocat. Saturday is often Caturday, with cat-themed floods of pics. Pictures of cats, along with any other domesticated animals, were generally not welcome on /n/ (now defunct, merged with /an/), and are still too often a sore point among /an/ frequenters.
Memes
Catgirl
Catgirls are largely mainstream in anime. Quite simply, A human female with cat ears and tail, sometimes oversized paws on their hands and feet. Catgirls are not considered furry in /b/, and similar lightly furred anthros are also considered "catgirls", such as the foxgirls.
Zippocat
Series of pictures potraying a real cat inquisitively exploring a shelf, and then being burned by zippo fluid. It is one of the more loathed images of /b/ because of its love for cats.
