Mounts and pets

[sklead]

I searched the forums here and didn't find anything specifically answering this question I have. I assume that it's already been thought of and/or done by now, but I can't find it (or lack the mental capacity to do so), so here it goes:

Is it possible to create your own mounts and pets in emu and if possible, then how?

i.e. Replace a mage's air pet with a bat or some other mob
or
Replace a drogmor or horse with a dragon for a mount or something.

Just wondering, was a little idea I had.