I see these 'cows' daily now... Not just Bonfire, but South Pole, and the Fluorite Plains. It's very annoying... I've blocked quite a few. They spam the chat and also 'buttswing' on top of each other. Like others have said before me, if you catch them doing this, report them, or just block them.
I've seen them a couple of times, mostly in Bonfire. They never actually annoyed me personally, and I would watch in amusement as they were cycled through Mate Center x3 That is the one thing I've really noticed; their like/dislike for Mate Center and the trolling they do there. I haven't seen buttswinging over other users as mentioned above, but they do:
-Mob the Mate Center character (sitting on top of them until there's just a blob of cows owo)
-Walk up to every member of the Mate Center trying to be their 'mate'
-And just generally trollolol around the island
(I am in no way encouraging the use of Mate Center, but this is what I've observed them doing there ^^')
On another note, the poor cows are probably really happy they got enough attention for a forum thread, or are now even Madder Cows. Ouo