If there is a Ditto mark instead of a regulation mark, the card has a sticker on the surface, and when you peel it off, Ditto will appear! Besides Bidoof, there are other cards that become Ditto when peeled off.
* Cards without stickers cannot be used at official competitions.
Source: Official Pokémon TCG site
Watch the Pokémon TCG: Pokémon GO Expansion Teaser Trailer
Pokémon GO combines with the Pokémon TCG this summer in an all-new expansion.
This summer, Pokémon fans will enjoy an exciting collaboration between the Pokémon Trading Card Game and Pokémon GO with the release of a new Pokémon TCG expansion themed after the popular mobile game. Check out this teaser trailer to get your first peek at what’s in store when these two games collide later this year.
Pokémon TCG x Pokémon GO Expansion Teaser Trailer 📍 🗺️
GO battle, collect, and trade with the Pokémon TCG: Pokémon GO expansion!
Watch the exciting teaser trailer about this expansion that brings the popular Pokémon GO mobile game into the Pokémon TCG.
*Cards vary by pack.
Announcing the Pokémon TCG: Pokémon GO expansion!
This summer, a collaboration between the Pokémon Trading Card Game and Pokémon GO will be released! The Pokémon TCG: Pokémon GO expansion will feature cards themed after the popular mobile game. You can get an early look at the expansion’s package design below.
More details will be released soon, so make sure to check back for the latest updates. For more information about the Pokémon Trading Card Game, please visit the official Pokémon TCG website.
Please be aware of your surroundings and follow guidelines from local health authorities when playing Pokémon GO. Upcoming events are subject to change. Be sure to follow us on social media, opt in to receiving push notifications, and subscribe to our emails to stay updated. For the latest on in-game events and feature updates, be sure to check this help center article.
—The Pokémon GO team
Source: Official Pokémon GO blog