Because they have a great sense of humor over there, and they're Rickrolling the shit out of everyone today.

For those of you unfamiliar with the concept of Rickrolling, it's a simple Internet phenomenon. People post a link to something that sounds really awesome or sexy (click here to see Britney Spears pick her nose! follow this link for Nigerian goat porn!) and then they link it to a URL for a Rick Astley video (typically it's "Never Gonna Give You Up"). You remember Rick Astley, right? The 1980s popper who looked like Howdy Doody and sounded like Michael McDonald? So anyway, the joke is that when you punk someone with the link, you can then say, "Oh, dude, you got pwned, I totally Rickrolled you."

So today, on YouTube, in honor of April Fools' Day, every single video link on their frontpage RickRolls you. No matter what you click.

That's one of the funniest things I've ever seen.