Here is a short guide on the surprise trades in Pokémon Sword and Shield. In the game, thanks to the new Comm-Y feature, you can exchange Pokémon or fight battles via Internet (also available in wireless local). If you see a "sticker" (see screenshot below) appear on your console screen during your adventure, it is a sign that another player is looking for someone to trade or fight. These stickers can come from your friends, but they can also be invitations from random players.
What are surprise trades?
Once in play, in your Comm-Y menu, you will have the opportunity to make surprise trades. This replaces the wonder trade of the previous versions of the game. Select a Pokémon you want to trade in your PC box and you're done! You will receive another Pokémon in exchange for yours. Note that it is impossible to know in advance which Pokémon you will receive after a surprise trade, but with any luck, you might receive a rare Pokémon!
How does it work?
The system will automatically find a trading partner for you while you continue to progress through the game, so you don't have to wait long minutes or do manual searches: everything is done without you having to worry about it. If your game is connected to the Internet, your trading partner can be anywhere in the world. It is also possible to receive a Pokémon from a nearby player via the local network.
A subscription to the Nintendo Switch Online service (for a fee) is required to participate in online trades and battles. However, you don't need a subscription to connect with other players on local network.