One of the things you can do with a Steam Deck is use it for emulation. Someone at Valve is evidently aware of this, given the recent Steam Deck video - which we wrote about two days ago - contained a shot of a Steam library with a Nintendo Switch emulator in it.
Oops. Valve have since deleted and re-uploaded the video with the emulator removed.
The icon only appeared in the video for the briefest of moments, but it was spotted by games tweeter Nibel. The emulator in question is Yuzu, an open source Nintendo Switch emulator. Emulation is legal, as long as you own the games and dump them to PC yourself, but it's still a murky area.
Perhaps someone at Valve was just experimenting with their device, or perhaps they just really wanted to play Metroid Fusion. They likely did not intend for the icon to be visible when they were capturing footage for this video, however.
We like the Steam Deck a lot even without having tried any emulation on it. As of this week, it's now available to purchase without a prior reservation, and its dock is finally available, too.