Merry Gear Solid: Secret Santa is a fan-created top down stealth action game in the vein of the Metal Gear series.

Merry Gear Solid: Secret Santa follows the story of Solid Santa, a hardened holiday veteran who must infiltrate several houses to deliver children their Christmas presents on Christmas Eve. Military security is at its highest due to recent terrorist activities, so delivering presents the conventional way is out of the question. Solid Santa must deliver them on foot, covertly entering the house through the front door and going undiscovered. The only catch is, there are some naughty, naughty children who are awake and expecting him! Not only this, but there are adults who are also awake and prowling the house. Luckily, adults don't believe in Santa, so they cannot see him unless he makes physical contact with them. Solid Santa must use stealth, along with other tricks, to avoid being spotted by the children and fulfill his mission.

Along the way, Santa receives help from not only his commanding officer, Major Tiny Tim, on Codec frequency 012.25, but also a mysterious informant who claims to be Santa's number one fan, referring to himself only as Santa's Little Helper. During the mission, Santa remarks that the information Santa's Little Helper is giving him isn't very helpful at all, and the informant remarks, "I'm only a little helper."

As the game progresses and Solid Santa finally makes his way to the top floor of the house to deliver his presents, Santa's Little Helper appears and reveals himself as Solid Snake. Snake tells Santa that after assassinating Big Boss in Outer Heaven, he was sent on another mission - to assassinate Big Boss' twin brother, Big Beard. Santa is perplexed until Snake reveals that Big Beard is actually Santa himself. Santa and Big Boss were both part of a project called the The Los Bigotes Perfectos project, a cloning project that was started in the 19th century by President Andrew Johnson. President Johnson was quite displeased with his lack of facial hair, especially after the abundant beard of his predecessor, Abraham Lincoln, and started work on genetically engineering the perfect beard. Two clones were born, Nick and Jack. One would be born the genes to the perfect beard, and the other, who would be aptly named Jack, as he would receive "jack."

After defeating Big Boss at Outer Heaven and destroying TX-55 Metal Gear, Snake and FOXHOUND would learn about Big Boss' twin brother, Big Beard. Not wanting to risk another Big Boss threatening the world with a nuke, Solid Snake was sent on a mission to assassinate Big Beard and end Big Boss' lifeline once and for all. Santa solemnly agrees to being terminated to allow Snake to finish his mission and better the world. His final words, "Happy Christmas to all, and to all a good night."