Pokemon Black and White card confusion...?

So, I'm trying to complete the Black and White set of Pokemon Cards. Well, I have a holofoil ducklett, but on the official car list, ducklett is not listed as being holofoil. I've been out of pokemon cards for a very long time, and I'm a little confused. Can any card be holo even if it not mentioned on the official card list? a card list reflecting any card variants would be greatly appreciated as well as an answer.