Uhhhhh.... I haven't updated the mod, so I dunno, but I'll bet it grows into a larger version of whatever it looks like. You probably have to feed it n stuff.
Very ****ing carefully if you dont want perma black screen. Just take out the creature files, bitmaps, sounds, AI and textures from the folder. For instance, you want to remove the bear. So you need to take out all listed above. But if you leave one thing belonging to the bear in, e.g the texture pack, you'll get black screen.
I just wiped the all the MC files and re-downloaded them, mostly because I hadn't backed them up. I think Mo Creatures isn't compatible with Fridays update or something, because a lot of my IRL friends are having the same problems.