The Alien Billboard is a treasure in Pikmin 2. The Alien Billboard is one of the 4 (PAL) or 8 (NTSC) treasures in the Ancient Ad series. It is in fact a Kiwi shoe polish container/lid. It is the 175th treasure on the List of Pikmin 2 treasures in the NTSC version and the 176th in the PAL version.
The location of this treasure varies from NTSC and PAL versions. In NTSC, the Alien Billboard is an early treasure and is on sublevel 1 of the White Flower Garden. In PAL, it is one of the late treasures, as a matter of fact, it can be the last treasure you can get before the arguable "final boss". It is located on sublevel 13 of Dream Den.
"There are several different patterns drawn on this object's surface. They appear to be characters or letters, but I can't make any sense of them. This is just an educated guess, but I wonder if this object is a kind of alien bulletin board? The size of the object seems about right for it."
"Perhaps this is some ancient billboard...but perhaps not. Its authenticity may be in question, but if you can use it for inspiration, you may become a topflight ad executive."