The question is a little lacking, I voted no.
Unicorn: If it's a horse with a horn on it's forehead, sure, not very weird.
Dragons: On firebreathing, not seen in the animal kingdom, so no, also because it's a bit ridiculous. On flying, slightly plausible, but with the bodyshape dragons are depicted with, physics don't add up. Way too heavy, and flimsy wings can't save that. Other than that, maybe, but then it's just a big-ass lizard.
Griffon: Well it's a mix between known species, and since educated people know that evolution isn't 2 completely different species making a combination, I'd say no to that as well. You could get something resembling, but stapling together various animal parts isn't how it works.
The game Impossible Creatures had that, and while fun, it's wasn't evolution.