Jessie and James arrive via their famous Meowth hot air balloon. Just like with the other members of the team, you can tap them and do battle with their roster of Shadow Pokémon. In addition to these new NPCs to do battle with, you can also outfit yourself like Jessie and James through new avatar items inspired by these two.
For now, Jessie and James are only appearing for a limited time, so if you want to battle them, you better do so before they blast off again.
[Source: Pokémon Go]