The official Japanese Pokémon Trading Card Game website has revealed a new type of card that will be included in the Pokémon GO set. Metamon cards in this set appear as other Pokémon. It will look like a normal Pokémon card, but on the surface of the card is a removeable sticker.

How to spot a Metamon

If there is a Metamon symbol in place of the regulation mark, the card has a sticker on its surface that when peeled off reveals Metamon! There are other cards besides Bippa that turn into Metamon when peeled off.
*Cards with the sticker not peeled off cannot be used in official tournaments.


Source: https://www.pokemon-card.com/ex/s10b/

YouTube Clip - Pokémon GO Metamon Cards

Source: https://www.youtube.com/watch?v=-2z9Vaztij4

Ditto

Now here's something you don't see every day… And if you're not looking closely, you might miss it! To find Ditto in the Pokémon GO expansion, look for other Pokémon that have a layer you can peel off to reveal the Transform Pokémon underneath! Note that the Pokémon that rests on top of Ditto can't be used competitively in official matches—only the Ditto itself. In fact, you'll find a little Ditto icon in place of the typical tournament registration mark!


Source: https://www.pokemon.com/us/pokemon-news/pokemon-go-expansion-more-iconic-and-powerful-pokemon-revealed/