Whenever Nintendo releases a new video game, there’s usually a free demo that they’ll also launch on the Nintendo Switch eShop. It is completely random when the company actually does this. Sometimes they’ll release the demo before the full game launches, and other times they wait until after instead. They also love to make a game demo available without any advance warning.
For example, earlier tonight, Nintendo decided to suddenly release a free demo for Donkey Kong Country Returns HD. The game had been officially released on the Nintendo Switch almost a month ago, on January 16th. You can find it on the Nintendo Switch’s eShop. A social media post relaying the news can be seen down below.

Hey! There’s gonna be a Donkey Kong Country Returns HD Tetris 99 Event!~ From 2/14 – 2/18!~
Just saw it via JP Nintendo Switch News Tab hehe :)
I AINT PLAYING THAT 😭😭😭😭😭
Me either, it’s too hard to play, I’m not a big donkey kong fan, but I still enjoy other games that feature Donkey Kong