As far as I know there are no combinations that make elves. The different elves you do see are either from promotional offers or they are dropped by bosses. As for mixing pets... Only a select few pets have a chance to mix. Even then they can only mix with other particular pets. Such hybrid pets are rare, you may need to hatch several times before the correct pets make a hybrid. I hear people saying they hatched five times and got one of the parent pets each time.
