Have you already finished Portal 2? If not, maybe you shouldn't watch this video, which shows you how to dig up three of the game's Easter Eggs, because at least one of them is seriously spoileriffic. In fact, you better stop reading right now, because we're going to explain what buried treasures are featured in this handy little video.
First, if you haven't spotted the location of the "missing experiment," better known as Aperture Science's Borealis, first hinted at in Half-Life 2: Episode Two, we'll show you where that is. Or, rather, was since the research vessel disappeared quite some time ago. If you're not familiar with the Borealis and its place in the Half-Life universe, the Combine Overwiki will get you up to speed.
Second, there's a portrait of a lady nestled away in Portal 2 that will help you put a face to an important name from Valve's new game. It's not hard to find—it's early in Chapter 7, by the way—but if you're without the related achievement, we'll show you how to get it.
Finally, of minor concern is one musical Easter Egg. If you recall, quiet rock band The National penned an original tune for Portal 2. Seems some people missed its location during their first play through, so we've included directions to that. Like it? You can easily find it on iTunes.