I just have an idea that you could combine two - four creatures and create your own unique creautre (obviously preset though) Sometimes the same combination wouldn't give you the same creature, but eventually it would. You could sometimes create really rare creatures and keep them at your home planet or release two into the wild to add that species to the planet you released them on. Seeing your creature that you made every now and then in the wild would give you a thrill, especially when it befriends you (because you created it) or sometimes attacks you (50/50 chance). Sometimes combining creatures would make a 'mistake'... No need to elaborate on that. Perhaps you may make a creature pregnant with your creation, this would make it more realistic. Also combining creatures would be moderately expensive. Sorry about spelling mistake in poll, I meant *keeping*.
It should be more like, the animals have pregnancy, and then they spawn a combined creature, however, with combining, it would take longer.
Maybe something like alien, a parasite (just an example) that uses other creatures genetic material to evolve.
That's too sci-fi! Combining creatures through machines or with normal pregnancy would be just fine! .
Well, for the sake of just subjective taste I'd prefer some sort of genetic recombinator machine more than the parasite. Especially as parasite suggests more complex system for the sake of the same effect. In generally though, I am ambivalent toward the idea. For it to really not be half-arsed we'd require either a gigantic load of new sprites for possible mutations or a whole new system for managing and customizing sprites so they'd allow sprites made out of different, nicely-fitting and smoothly moving during animation elements. It could very much be - depending on how hard it would be to implement said things - additional months of development for the sake of having some mutated penguin or some other thing. If something like that would be to be added, I'd rather have in some version far in the future after initial release so the more vital stuff gets to be put in. Played a lot of Elona, eh?
Perhaps something like the Fusion system from Monster Rancher? You get the body of one with the traits of another, and a different percent chances to get different things, which are displayed in a readout before you go through with the fusion. (Side-note: That game was better than a lot of people give it credit for.)