The Four Giants are four fictional creatures in The Legend of Zelda: Majora's Mask for the Nintendo 64. They are very large and orange, and each have a beard and a pointy nose. They have deep voices and they are worshiped at the Termina Carnival for good harvest.
The Legend of Zelda: Majora's Mask
At the end of the game, Link will befriend one of the giants, and will then be able to summon all four of them to push the moon back before it hits Termina.
They used to be worshiped as gods but now the sleep in a realm of sanctuary which is covered in green falls of fog and green clouds and tiny bubbles floating around. They are the creators of Termina (Hyrule's mirror dimension) and are essentially equivalent to the three goddesses in Hyrule. Link summons the Four Giants by playing a tune on the Ocarina of Time. The song he plays is called the Oath to Order.
Super Smash Bros. series
In the Termina stage in Super Smash Bros. Melee for the GameCube, the Moon will gradually inch closer and closer to the ground in the background. At the last minute, the Four Giants will appear and push the moon back into the sky. This will repeat every few minutes until the end of the battle in the game. A trophy of the Four Giants also appeared in the game, the description of which can be seen below.
"Swamp... Mountain... Ocean... Valley... The four who are there..." Link summons these four giant guardians to aid in his battle against the Skull Kid, who's possessed by Majora's Mask. They appear from the four compass points to catch the moon, which is about to crash into Clock Town. Without abandoning the innocent Skull Kid, they're able to protect the town."