X is for...

X-Ray Fish?

I don't even know if that's a real animal.  Not to mention that X-Ray isn't even x-ray in German.  It's some guy's name.

I tried really hard to find a good X animal, but unless you use the latin name for whatever scientific classification something is (which doesn't sound very kid-friendly to me), it appears there are no animals that start with X.  Maybe I could just throw a xylophone in there and pretend it's an animal.  If you were a little kid, would you notice a xylophone wasn't an animal?  Probably not.  There.  Never mind.  Problem solved.  X is for xylophone...