As chronicled in Rosalina's Story, Luma was first met by a young Rosalina near a rusted spaceship; he explained to her that he was awaiting his mother, who was coming for him on a comet. Rosalina promised to wait with him, and the two eventually repaired the spaceship with the intent of using it to search for her themselves. As the pair travelled through the cosmos, they came across a comet made of ice and, though there was no sign of Luma's mother, decided to remain on it as they continued their search. One night, after dreaming of her own mother leaving her, Rosalina took Luma in her arms and adopted him as her own, promising to take care of him herself from then on.
Using materials they found frozen beneath the comet's ice, Rosalina and Luma constructed a house for themselves. Following the arrival of more of his kind from a nearby planet, Luma began to fight with them over Rosalina, who proceeded to welcome them into her new home and give names to them all. Some time later, when reminded of her former home and family, Rosalina became saddened once more - to cheer her up, Luma reminded her that her mother would always be a part of her and transformed into the Beacon, so that she would have a way of visiting her home planet every 100 years.
Super Mario series
Super Mario Galaxy
Many centuries later, Bowser attacks the observatory and steals the Grand Stars it requires to function - it is presumed that during the confrontation, the reborn Luma was knocked from his home and fell to the Mushroom Kingdom below. Luma is then found by Princess Peach, who invites Mario to her castle during the Star Festival to show him her discovery. After Mario is sent flying off into the cosmos by Kamek's attack, Peach sends Luma after him as her castle is towed away by Bowser's forces to the center of the universe.
Luma is formally introduced to Mario when he awakens on a planet within the Gateway Galaxy - after giving him a brief tutorial and a game of hide-and-seek, the star child determines Mario may be capable of helping Rosalina and joins him at his mother's request, taking up residence beneath the Mario Cap and in the process granting him the Spin maneuver. Together, the two make their way through numerous galaxies and slowly reclaim the lost Power Stars, eventually returning enough power to the observatory's Beacon to allow themselves access to Bowser's Galaxy Reactor, where Mario uses Luma's powers to defeat the Koopa King once and for all.
Following Bowser's defeat and the rescue of the final Grand Star, the star it had already begun to form implodes on itself due to a lack of power - the ensuing black hole begins to rapidly consume the entire universe. Luma then appears from the Mario Cap and, after a wave goodbye, flings himself into the heart of the catastrophe, and is followed by the other Lumas. Their efforts succeed in stabilizing the black hole, destroying it and restoring the cosmos to their former state.
After the player collects all 120 Power Stars and defeats the final boss once more, a secret ending is displayed, in which Rosalina is shown thanking the player and promising to watch over them from beyond the stars before departing from the Gateway Galaxy in the observatory. The scene then shifts to the dilapidated spaceship from her storybook, with Luma peering out from inside; he waves once more at the camera before rising up toward the stars and out of sight.
Super Mario Galaxy 2
Luma makes his second appearance in Super Mario Galaxy 2, where he is called Baby Luma. He is found in the prologue of the game lying on the ground and immediately takes a shine to Mario. Baby Luma flies into the Mario Cap, and Mario's body begins to tingle, giving him the power to spin. Mario later meets two other yellow Lumas, which call Baby Luma "young master Luma" and send Mario off to the Sky Station Galaxy.
After Bowser is defeated, Mario returns to Starship Mario with Princess Peach and the Grand Star, after which Rosalina appears in her Comet Observatory. She explains to Mario that she knew all along that she would someday be reunited with Baby Luma, because there is a power even beyond that of the stars that governs the destiny of them all. After promising that he will never ever forget about Mario and taking the Mario Cap as a souvenir, Baby Luma rejoins Rosalina and leaves with her.
Baby Luma, alongside other Lumas, appears in Super Mario-Kun volume 38 after Mario lands on a planet after he is swatted away by Bowser. He wants to play with Mario, but Mario does not want to do anything, after Mario loses his confidence. Just after Baby Luma tries to encourage Mario to get up and save Peach, a giant Goomba comes. Baby Luma wants Mario's help, though Mario refuses. Rosalina pops up and encourages Mario to fight the Goomba. Mario then learns the Star Spin technique and defeats the Goomba, who turns out to be just an illusion created by Rosalina to help Mario regain his confidence. They team up and help each other as the adventure progresses.
In this adaption, Baby Luma calls himself "A Star Child". He is also given a mouth, mostly to illustrate facial expressions better. The cover also depicts Baby Luma as a yellow Luma instead of a cream-colored one.
Mario Golf: World Tour
Super Smash Bros. series
In Super Smash Bros. for Nintendo 3DS, Super Smash Bros. for Wii U, and Super Smash Bros. Ultimate, Rosalina and a Luma are collectively playable as a singular character. While the first Luma spawned during battle will always be yellow in color, one of the alternate colors for any subsequent Lumas spawned during the match is modeled after Baby Luma. This character is also present in Super Smash Bros. for Wii U in the form of a trophy, which can be obtained when it appears at random in one of the game's single-player modes.
Mario Sports Superstars
Due to Mario Sports Superstars reusing Rosalina's golf animations from Mario Golf: World Tour, Baby Luma reappears in this game in the same capacity.
Sprites and models
Super Mario series
Super Mario Galaxy
Super Mario Galaxy 2
Super Smash Bros. for Wii U trophy
Names in other languages