Moai

The moai is a recurring Easter egg in the Final Fantasy series, appearing in unexpected locations, usually on World Maps far from important locations, and having little to no function whatsoever. In most cases, they are a reference to the, monolithic human statues from the Chilean island of Rapa Nui (Isla de Pascua).

Final Fantasy IV
A stone appears on the Red Moon. This one is an allusion to the infamous myth rather than the moai. A "happy face" crater and rock formation, inspired by the, also appears.

In the Game Boy Advance version, the Lunar Ruins open in front of the stone face once Zeromus is defeated.

In the DS Remake, if the player stole Dark Matter from Zeromus and uses it on the Stone Face, they will fight Proto-Babil.

It is the new location of Golbez's second Challenge Dungeon in Final Fantasy IV: The After Years.

Final Fantasy V
A moai appears at the bottom of the ocean. It serves no other purpose than being an Easter Egg.

In the Game Boy Advance version, it is revealed that the moai is in fact a structure constructed by the Ancients, used to transport people from the "Real" world to that of the Sealed Temple, and disguised to look like a relic from some long-lost civilization. The device was sealed off however, and only became accessible due to the recent earthquakes.

Final Fantasy VII
A moai appears on a cliff in the Great Glacier, while other moai statues appear in the Chocobo Racing Arena. This is the first time stone faces appear in locations rather than world maps.

Final Fantasy VIII
In PuPu's sidequest, the UFO? enemy is sometimes seen abducting a stone face with its light beam. Additionally, colored stone faces are involved in the Obel Lake sidequest, though no graphics are shown for these.

Final Fantasy IX
At the outset of the adventure, the Prima Vista crashes into the Evil Forest and Zidane is left to make a big decision. After recruiting the help of a Knight and Mage, Zidane and company travel into the dark depths of the forest to save the Princess who holds his recent affection. Hanging left at the first fork will take the player to a serene waterfall glowing in the evening Mist. On the right side of the background is a tall moai, looming as high as the locale's alpine treeline. This zone is unique: aside from a trivial command prompt and the Easter egg, it is an itemless dead-end that holds no practical purpose in the game whatsoever.

Final Fantasy XIII
At The Gapra Whitewood, at the "Maintenance Exit" past the save point, in the background you can see what resembles a moai face on one of the buildings in the north. Afterwards a scene reveals this is a building in Palumpolum, but it clearly resembles a moai face.

Dissidia Final Fantasy
One of the player icons is a moai from Final Fantasy V.

Fortress
A moai appears in a forest in concept art for the game.