What did I just watch?
It's called a Rickroll!
Rickrolling, alternatively Rick-rolling or Rickroll, is a prank and an Internet meme involving an unexpected appearance of the music video for the 1987 song "Never Gonna Give You Up," performed by the English singer Rick Astley. The meme is a type of bait and switchusing a disguised hyperlink that leads to the music video. When victims click on a seemingly unrelated link, the site with the music video loads instead of what was expected, and they have been "Rickrolled". The meme has also extended to using the song's lyrics, or singing it, in unexpected contexts. Astley himself has also been Rickrolled several times.
The meme grew out of a similar bait-and-switch trick called "duck rolling" that was popular on the 4chan website in 2006. The video bait-and-switch trick grew popular on 4chan by 2007 April Fools' Day and spread to other Internet sites later that year. The meme gained mainstream attention in 2008 through several publicized events, particularly when YouTube used it on its 2008 April Fools' Day event.
Astley, who had only recently returned to performing after a 10-year hiatus, was initially hesitant about using his newfound popularity from the meme to further his career but accepted the fame by Rickrolling the 2008 Macy's Thanksgiving Day Parade with a surprise performance of the song. Since then, Astley has seen his performance career revitalized by the meme's popularity.