Ferrets and rabbits: haven't been there myself but from what I have heard
from others it can be doable depending on the personalities involved, but
it's unlikely.  There are individuals for whom it works.  On Marc Marpone's
show he's got Splash the ferret who also once appeared in a ferret mag with
one of his bunny pals.  I've seen that ferret (on air) snuggle down with a
rabbit, try to share food with a rabbit, etc.  Have also seen him do the
same with some types of large rodents, and some large birds.  The guy was
asked once about that on the air and he said that the rabbits and ferret
together should be seen as quite unusual, but with the large rodents must
be seen as more unusual than with rabbits, and with the birds is virtually
impossible -- that Splash is the only ferret he's had who gets along with
large birds (well, too).  Even with Splash he keeps reptiles, small birds,
small rodents, etc.  protected.  I can recall someone here on the FML,
though, who once walked in the kitchen and wondered why the ferret was
placing nummies from the food bowl off to her side, only to look and find
that the ferret was patiently feeding a mouse bit by bit.
 
Basically, it's not simply impossible, but it's not as probable as some
other mixes.  You are likely to hear from some of the FMLers with info;
know a few list members have or have had the two together.  Know you'll
use care and that you know that you might have to use care with the cat
and dog in relation to the rabbit, too.  Either one also stands a chance
of being dangerous to the bun.
[Posted in FML issue 2998]