Not sure if my kids did something or if someone sat on the remote and butt-clicked, but every video displayed by the YouTube app on my Shield TV now has an overlay showing video codecs, dropped frames, etc. I didn't find anything in the "Settings" tab that seemed on-target. Rebooting didn't help. Am I doomed for eternity to see this extra nerdy data on all my nerdy science videos?
I'm not at home so I can't guide you step by step but play a video, press a button to see options on screen. Look for stats for nerds or something like that and then it off.