EarthBound 3: Unity of the Dimensions, called Mother 4: Blue Story (MOTHER4：ブルーストーリー, Mazā 4: Burūsutōrī) is the fourth installment of the EarthBound/Mother series. It is a crossover with the Super Mario series and is rated E 10+ for cartoon violence, crude humor, and mild suggestive themes. It is for the Wii U and Nintendo 3DS.
Not too long ago, a boy named Lucas defeated the Pig King, Porky. Since then, King Porky had be trapped inside the Absolutely Safe Capsule...Until now. Having been traumatized by all of the events he had endured and caused, Lucas and Ness decided to free him from the capsule and restore him, with the help of Rosalina (unbeknownst to them). Now, for Porky to have a second chance at life, he must join Ness, Lucas, and the Mario Bros. to stop Bowser's new plan to use the Ahkoo Amulet to take control of the Mushroom Kingdom and Eagleland.
- Mario-The hero of the Mushroom Kingdom, and the main protagonist alongside Ness.
- Luigi-Mario's brother and a secondary protagonist.
- Ness-A determined boy from the town of Onett. He shares the postion of main protagonist with Mario, and has recently made amends with Porky.
- Lucas-A sensitive boy who defeated Porky in Mother 3. He and Ness have forgiven Porky, and Lucas is often the one to help Porky in trying to be nicer and more heroic.
- Porky Minch-Ness's childhood friend, and a former bully/villain. He has been given a second chance at life, and has made amends with Ness and Lucas. He looks up to Rosalina for guidance, and sees her as a role model of sorts. Despite his second chance, he is very insecure and regretful.
- Princess Rosalina-A cosmic princess who gave Ness and Lucas the strength to save Porky from the Absolutely Safe Capsule. She has informed Ness and Mario of the impending danger of Bowser obtaining the Ahkoo Amulet.
- Princess Peach-Princess of the Mushroom Kingdom and Mario's love interest. She can give hints regarding tasks and missions.
- Jeff Andonuts-Ness's friend from Twoson. He can supply the player with weapons and items.
- Bowser Koopa-An evil king who is (usually) Mario's enemy. He has obtain an ancient amulet called the Ahkoo Amulet, which can personify the negative traits and insecurities of an individual and cause them to take over their body; Bowser uses this to threaten both the Mushroom Kingdom and Eagleland.
- Bowser Jr. and the Koopalings-Bowser's son, alongside his seven "adopted" children/minions. They act as minibosses on some missions, and are bent on keeping Mario and Ness from the Ahkoo Amulet.
- Princess Penelope-Rosalina's identity under the influence of the Ahkoo Amulet; after the protagonists have obtained it, Rosalina is lured in by the amulet itself to wear it, and as a result, her darker side takes over and threatens the very galaxies she rules. She is ultimately defeated when she learns how much Porky admires her and cares about her.
- The Japanese name for the game, Mother 4: Blue Story, comes from the fact that Porky and Rosalina-two characters who play a major role in the story-wear blue; as a result, blue is also commonly used in the game.
- Some translations rename the game EarthBound and Mario, to reflect that the game also features Super Mario characters.
- Penelope's nature and powers are heavily reflected from that of Giygas, the antagonist of the first two EarthBound games.
- Additionally, the Ahkoo Amulet's influence on those who wear it is similar to the Mani Mani Statue's (possible) influence on Porky in EarthBound.
- The Ahkoo Amulet's name is a corruption of its Japanese name, the Aku Amulet, which literally means "Evil Amulet".
- The French and Italian translations call the amulet the Rosetta Amulet, a reference to Rosalina's Japanese name, Rosetta, as well as the Rosetta Stone.
- In Greek mythology, Penelope was a woman who remained faithful to her husband while he was absent during the war. This makes Princess Penelope's name meaningful in two ways: it's ironic, as she is the result of Rosalina's (unintentional) betrayal, and this reflects Rosalina's own fears that someone (if not everyone) she loves will betray her.
- In Japanese, Penelope's name is Princess Echo; Echo was a nymph who fell in love with Narcissus, whom she waited for when he left her and never returned. This name reflects Rosalina's insecurity that the people she loves will leave her behind and never return for her.
- Some translation of the game do not give this form of Rosalina a different name, making her seem less like an individual entity and more like a truly corrupted Rosalina.
- It is unsure whether or not the game is considered canon, as there are hints of both. This was done so that relevancy to continuity could be determined by individual players.