It first appeared in the PSX Abe's Oddysee demo. It was cut from all future retail releases of the game due to level design changes. It returns in the remake of Oddworld: Abe's Oddysee in pre-alpha footage as a poster on the floor of RuptureFarms. It's currently unknown at this time if it'll make it into the final version of the game. It does in fact make an appearance in the final version of Oddworld: New 'n' Tasty on the billboards at certain times.
It also appears in The Art of Oddworld Inhabitants: The First Ten Years 1994-2004 on page 57.