One of Google's cleverest Easter Eggs is letting you play Snake while watching a YouTube video. You used to be able to trigger that by holding down the left arrow key for two seconds, but now that YouTube uses arrow keys as fast forward and rewind controls, that doesn't work. Here's how to get the same effect.
It's fiddly and not always reliable, but I got pretty good results by ensuring that the video had focus (click once to pause and again to play), then holding down the Up and Left cursor keys simultaneously. Snake! If you find a simpler or more reliable approach, share it in the comments.