YouTube hasn't ever been one to skimp on the Easter eggs, but this is a new one for me.
It's hidden away on the timeline that charts your progress through a video. If you highlight that timeline and hold left — either left on an attached game controller, or the left arrow key — in certain versions of YouTube (I'll get to that in a minute), you can summon a dog.
It takes a bit, so be patient. If you've watched any of the video, it'll rewind first. Then you want to keep holding left for another 10 or 15 seconds. Eventually, a little, brown dog, possibly a Corgi, will trot across your timeline, from left to right.
The Easter egg only works in certain versions of YouTube, as far as we can tell. We've tested the three major console apps — PlayStation 4, Xbox One, and Switch — and the dog is there in all of them. It's also accessible on your PC via web browser, but only using the YouTube TV interface.
(I'm not sure who first discovered this Easter egg, but I first spotted it right here on the Nintendo Switch subreddit. When I tried googling "YouTube Easter egg dog" I fell down a completely different, and admittedly excellent, rabbit hole.)
The standard YouTube.com won't work. Instead, you have to go to YouTube.com/TV. After the sign-in page (you can skip it), select any video you see and follow the instructions above. If you're not using a game controller, you can use your arrow keys to navigate the interface and highlight the timeline.
Here's some video showing how it works on a Switch.
The Easter egg doesn't appear to be specifically connected to the YouTube TV; there are separate Xbox apps for YouTube and YouTube TV, for example, and I got this pup to show pop up in the former. But the YouTube TV-style interface seems to be key. The Easter egg doesn't work on the standard website, and it doesn't work in the YouTube app on my Pixel XL.
It's cute though! Who can possibly be mad about having one more secret, smiling dog in their life? This is great news.
Now, go fetch your YouTube timeline and see this surprise for yourself.