The Ultimate Jackface is a meme from the Lostpedia Forums in which the member JoeyeoJ discovered a moment in the penultimate Lost episode "What They Died For" in which Jack Shephard, played by Matthew Fox, looks directly at the camera. The original poster continued to post various pictures, including Lost screenshots, in which the face is inserted into the shot. Sometimes text is included and sometimes they are in a multi-panel form like a Dinosaur Hed, a similar meme from the Lostpedia Forums. Other members of the forum have also taken to making these. The name references the various faces that Matthew Fox makes while playing the character of Jack, which have become known as Jackfaces.
Have you seen the Ultimate Jackface yet?
No, what is it?
Dude, it's crazy! Foxy looks directly at the camera!
He breaks the fourth wall? In Lost?! I gotta see this!