Where's Waldo, is a screamer that was uploaded on Albino Blacksheep. In the game, the "player" needs to find Wally/Waldo in the image, and when the game is started, a cheerful circus music is played. However, after 41 seconds, a picture of Pazuzu suddenly pops up along with an extremely loud scream.
The screamer became so popular in Japan that a NicoNicoDouga(a famous japanese video-sharing website) user created a Vocaloid song about this screamer in 2010. The music talks about how angry Wally were because someone(in this case, you) were searching for this screamer.
NOTE: The following flash contains a screamer.