If you are a YouTube fanatic or have friends who are, it is likely that at some point in the last few months you have been Rick-rolled.
For those of you who don't know what being "rick-rolled" is, here is an explanation of the phenomenon from Yahoo answers:
An internet prank or joke. Rick Roll, Rick Roll'd or Rick Rolling is an internet spam trick in which people post a link to a Rick Astley video on Youtube, but say the viewers of the video are being led to another video, usually proof of unconfirmed gaming news or trailers.
For example, a friend sends you an email saying "Hey, check out the new Harry Potter trailer here!" You click the link and end up on YouTube watching Rick Astley's "Never Gonna Give You Up" video.
Today on Twitter while reading tweets, I got Barack-rolled. Check out the video here. I'm sure this will get a few million views by the end of the week.