Guys, check out this mod coming Friday:

It's like Mo'Creatures, but with much more original and balanced mobs- better AI, better atmosphere and spawning code, better models.
Here are the mobs included in Friday's update:
Tortoise:
The tortoise can be somewhat tamed by feeding it flowers, in exchange for a free meal, the tortoise will gladly shoulder the burden of a chest, increasing your mobile inventory! Plus, they're cute as hell!
Troll:
The troll is a terrible beast that comes out at night to hunt. It fears the sun, which turns the troll in to stone! Beware the rocks that it throws!
Fox:
The fox is a fluffy and agile creature that makes a good companion.
Grove Sprite:
The grove sprite is a mystical creature that thrives in the hearts of dense forests. It lives to spread trees, which it views as brethren. They are peaceful, but don't anger them. You've been warned!
Some more mobs coming in future updates:
Armadillo:These creatures roam the desert and shrub-lands munching on bugs and some shrubbery. To protect themselves from predators, they have thick armor plating all along their back and will roll into a nice ball when attacked. This makes them difficult to hunt, but a persistent hunter will claim his prize.
Golem:The Golem is an artificial creature that would be created to serve it's creator. Unlike living beings the Golem cannot think or problem solve. It is given a single command and it will execute that command until it is destroyed.
Hag:These ferociously malevolent beings dwell in the deep waters that fill swamps, as well as occasionally in lakes located in deep forests.
Salamander:The salamander is a docile denizen of the Nether. They dwell around large lava pools and take breaks on the shores to cool and relax. Normally disinterested with the humans, a salamander will defend itself if attacked. They are strong and breath fire when desperate.
Plus lots more!