First of all, let's just quickly revise what we (think we) know about species. It is surprising how many of us doesn't know how to define species exactly. So here's a little help – officially, one specie includes all the animals who can reproduce and have fertile offspring, with the fertile offspring being the key words. In most of the cases those animals look alike, but not necessarily. And all goes according to the plan when animals inside a specie procreate, but sometimes, no matter how beautiful and cute their offspring can be, they cannot procreate further. I agree that it would be too many possibilities if they could, but just look at what we already have. That 'dead end' in the cross-species procreation are infertile, but immensely beautiful animal hybrids. Let's take a look.
Thanks to Napoleon Dynamite, we are all familiar with liger – an offspring of male lion and female tiger. They are definitely the largest cats in the world (they are bigger than both their parents). They picked up some of the best characteristics of both lions and tigers, but unfortunately they are only bred in captivity.