Justin Kerprank is a reality television personality who hosts the self-titled series Ker-Prank'd.
The TV shows a surgeon about to cut into his patient when suddenly Justin Kerprank jumps out from behind a fern and yells "KER-PRANK!"
Later when Mabel and Dipper realize that Stan has been lying about who he really is, Mabel suggests that they are being "Ker-Prank'd," and that Justin will jump out from behind one of the plants to reveal that it's all just a joke. This, of course, fails to happen.
- He was also seen at the end of the "Not What He Seems" countdown/live stream on the website "The Mystery of Gravity Falls."