Hmmm... MUCK used to be a particular type of MUD, Multi-User Dungeon. Basicly, they were text based online multi-player RPGs, to which players connected via telnet. There were usually also chat capabilities, so they often also had a social network grow up around them, sort alike BBSes. They were the precursor to todays MMORPG (Everquest, World Of Warcraft, etc). Apologies if you knew all of this.

Anyhow, perhaps FurryMUCK was a MUCK that catered to furries? I'm resisting searching just in case...

Anyhow, the images:

http://gtf.org/ram/smile/sloth9.jpg
http://gtf.org/ram/smile/babyotter.jpg (I visited these in my browser to test, and the baby otter made me giggle involuntarily again!)