Redditor BlueMaxima shared this Nyan Cat Easter egg with the board a few days ago: Assault your eardrums with endless Nyan Cat, and you will be rewarded with a karaoke mode. According to his tally, it takes almost 3,000 seconds, which is close to 50 minutes. It’s just as well; it took me about that long to get the melody down.
The exact time to trigger karaoke seems to vary from user to user; I went past 3,000 seconds and never saw the button that apparently appears on the righthand side of the screen. If you don’t want to try your luck there, then play around with the “Lower Volume” button — but only if you have a high tolerance for bright colors and high pitch.
Here’s a video of what it looks like. It looks as if the words fill in themselves like a standard karaoke machine.