What do the purple Oaken cards do in Frozen Uno?

Question

I found this set of Frozen Uno at an op shop with no rules included. Most of the cards are just a Frozen version of normal Uno cards, but we can't work out what the two purple Oaken cards (in the bottom row) are for. I looked online, but the sets pictured don't match the one we have. Does anyone know what they do?

(Apologies for the upside down +2 card. I didn't realise until posting that it was upside down.)

Edit: I don't think this is the same as the blank purple UNO cards that the other question has suggested. For starters, it's not really blank, and there's nowhere good to write down a value to use it as a replacement. And there's only 2, as opposed to 4 which the question states comes with a regular UNO deck.

Answer 1

The purple cards are not mentioned in the UNO Disney Frozen's rules so it could be 2 additional blank cards that could be used as a replacement card or a house rules card, like mentioned in the UNO rules from 2001.

What are these extra cards for?

Blank Card - This is a special card that you may use in one of two ways. If a card from your UNO deck is lost or damaged, you may use the Blank Card as a replacement.
Example: If you find that your deck is missing one of the yellow 7's, you would simply replace it by taking the yellow Blank Card, marking a "7" on it and adding it back into the deck.

If you family has a special UNO rule you prefer to play with, you may write that rule on the Blank Cards and add them straight to the deck.

Answer 2

They appear to reuse the same art as the Disney Frozen Uno cards, but neither I or II have the same colors or the same image for the same card. Searching for the top card, I found Online Store, where they are out of stock. It is not marked as Disney and probably not an official version.