Nintendo has posted a call for 10,000 testers who’ll get first access to an unnamed, mysterious Switch Online feature. The whole posting is rather vague and offers no solid clues on what feature it’s testing exactly, but only people who have an active Nintendo Switch Online + Expansion Pack membership can participate in the “Playtest Program.” Nintendo’s $50-a-year Switch Online Expansion Pack adds Nintendo 64, Sega Genesis and Game Boy Advance games to the subscription service’s games library. It also gives users free access to downloadable content for Mario Kart 8 Deluxe, Animal Crossing: New Horizons and Splatoon 2.

Testers must also be at at least 18 years old and must have an account registered in Japan, the US, the UK, France, Germany, Italy or Spain. Switch Online subscribers who want to participate can send in an application by scrolling to the bottom of Nintendo’s announcement and clicking the “To Application Page” link.

The company will start accepting entries today, October 10, at 8AM PT/11AM ET, until November 5 at 4:59PM PT/7:59PM ET. Nintendo will choose participants in Japan through a raffle if it receives a lot of applications. Everyone else may want to hurry if they want to participate, because it’ll be first come first serve for them. The company will also stop taking applications early if it quickly reaches the maximum number of participants.