when you see it
"When you see it, you'll shit bricks."
A meme format which refers to something in a picture which may not be seen so easily or subtly hidden. When seen, it may come as a shock to the viewer.
The Japanese equivalent on Pixiv is "おわかりいただけただろうか" or "お分かりいただけただろうか" (Owakari Itadaketa darou ka, 'Do you understand now?'). This phrase is from a horror TV show, "ほんとにあった! 呪いのビデオ" (Honto ni Atta! Noroi no Video, 'Cursed Videotapes Really Exist!'). When the TV staff replayed ghost videotapes sent by audiences, the phrase was used.
The exact origin of the phrase is unclear, but it likely originated from 4chan.