"It's the perfect counterpoint to the Puyo Puyo mash-up and the VR chill of Effect."
It comes as part of the free-to-play game's 23rd Maximus Cup.
If you earn 100 event points by July 13 you can permanently unlock this theme.
Players will have a chance to unlock the theme March 4-9.
The event is set to run January 7 -11.
The event will be held December 4 - 7 and players can unlock the theme permanently if they secure enough points.
Tetris 99 players can now earn a Paper Mario theme for the game by playing the game and earning points in the new event.
Nintendo recently announced that it's sending its lovely life sim Animal Crossing: New Horizons on a field trip to the realm of Tetris 99.
The Maximus Cup is about to start on Friday with Ring Fit Adventure-inspired rewards as prizes.
The online block 'em up has a new way to play that also features in Grand Prix 10, with 999 players set to win a prize.
Tetris 99 players will be able to unlock a Switch-exclusive theme for the game during this month's newly announced crossover event.
The third Grand Prix event starts next week too, with the offline DLCs included in the Big Block season pass.
Here are 10 ways to improve your chances at winning a game of Tetris 99 on Nintendo Switch.
The Grand Prix this week has big prizes at stake, as those who win can get these points to spend in the eShop.
Ninety-nine tetriminoes get dropped onto an island and will have to fight to be the last one standing. We would love to finally kill the C-piece, but that's not quite the case.