When you see it
From Screamer Wiki
When you see it, also known as shitbrix, mind games, and Mind Fuck, are another type of screamer created in around 2008. The creator who started it remains anonymous. The screamer was so popular, it even became an internet meme.
The concept is pretty similar to What's Wrong; the objective is to get the viewer to look closely at an image that appears normal at first glance and to claim that upon closer inspection, they will find something frightening or disturbing. But when the viewer is focused on the image, a screamer will appear on the screen and scare the viewer. These screams generally come in the form of animated GIFs that are meant to be still imaged. Due to them being GIFs, the rest of the screamers are quiet.
At around 2008, an anonymous user would post the "when you see it, you shit bricks" gif, starting the origin and making a little spread. After a while, it got famous and became an internet meme due to how scary it was to post. After a while, the shitbrix.com web registered. Way after, the Jeff the Killer GIF was made and got famous. It even was featured as a giphy on Steam.
NOTE: The following links contain a screamer!
- Collection of Pictures: shitbrix.com