Rufus McCallister (also known as Mother Doomsday) is an owner of the Ninjago Doomsday Comix store, where he assists customers with his vast knowledge of comic books.
When the ninja were turned into kids due to the Mega Weapon, they realized that the Grundle had also been revived by Lord Garmadon's spell. They asked Lloyd for help, so he immediately brought them to a comic book store. There, they met Rufus McCallister (as Lloyd tells them, otherwise known as Mother Doomsday), a man who has knowledge of extinct or nonexistent monsters. He thought that their questions about the Grundal were theoretical, but still told them all he knew of the creature. He recommended using an illuma-sword to repel the Grundal, as it disliked light but also stated that illuma-swords must be won in a comic book trivia contest.
Although Lloyd entered the competition, he hadn't read the latest issue of a sold-out comic book, which cost him the victory. At that moment, however, the Grundal appeared above the comic book store, forcing the ninja to reveal that their questions weren't theoretical. The creature came crashing down in front of a stunned Rufus, and the ninja grabbed the illuma-swords, but the weapons broke easily when they hit the Grundal with them due to them being props. As the ninja immediately assumed they were doomed, Master Wu and Nya arrived, throwing the Tomorrow's Tea over to them and instructing them to use it in order to age the Grundal as well as themselves. Though the ninja were hesitant at first, Lloyd is forced to use the tea.
With the Grundal gone, the ninja are back to their normal ages, but Lloyd had grown as old as his teammates. Upon seeing his age difference, Rufus realized they were the real ninja and offered to give him a copy of the comic book Starfarer as a token of gratitude, though Lloyd declined, claiming that he knew how the book ends.
When a Stone Warrior attacked Ninjago Doomsday Comix, Rufus attempted to retaliate with an illuma-sword. His efforts were in vain against the enemy, forcing him to retreat with his comic books.
The ninja were forced to leave Ninjago City, most of the team saying their goodbyes, though, Zane began feeling left out as he had no one, in particular, to wish farewell to. Sensei Wu pointed out to him the crowd of fangirls who excitedly surrounded the Bounty from the harbor, Rufus bursting out from them and admitting that he will miss the White Ninja.
After the ninja went on a believed crime spree, Rufus was interviewed by a news channel and told them he was ashamed that he wore their underwear, before realizing he had admitted that on-air.
He makes a small appearance when Master Wu took away people from Djinjago falling.
Rufus served as a DJ for Cyrus Borg but unintentionally annoyed him with his repeated mistake.
Rufus, surprised, watches as Lloyd tells the citizens to stand up against Garmadon. He exclaims a reference to something, and when no one around him understands, he mentions he is going out of business.
When a piece of debris nearly falls on him, Kai, who was nearby, fires a chain, saving him before he is struck. As Kai flies away on a Fire Dragon, Rufus is seen saying, "Superheroes do exist."
- The back of his original shirt says "COMIC MELTDOWN".
- He is credited as Rufus McCallister in seasons 4 and 6 and Mother Doomsday in his other speaking appearances (except when he was uncredited in "The Day Ninjago Stood Still").
- The lines on his shirt indicate that he is overweight, but in Season 9, his shirt has no lines, indicating he may have lost some weight.
- In one of the official descriptions for "The Day Ninjago Stood Still," he is referred to as a comic book writer. It's unknown if this was an error or if he does in fact also write comics.
- He is one of many characters in the TV show whose first set appearances are in The LEGO Ninjago Movie sets, the others being Ed, Edna, Mystake, Patty Keys, Sally, and Noonan.
- He was the DJ at the Borg Store.
- In "The Corridor of Elders," he used an illuma sword to fight the Anacondrai.
- Rufus shares some similarities with The Simpsons character Jeffrey Albertson, aka Comic Book Guy. Both own comic book stores, are overweight, have beards, have collectors items, keep replicas of light swords, and have ponytails.
- In Season 9, he no longer wears his "Mother Doomsday" t-shirt, and now wears the same "Galidor" t-shirt and jeans from his appearance in the 70620 Ninjago City.
- He somehow gained ownership of the plans for the Destiny's Bounty.
- His minifigure uses Clouse's hairpiece despite his TV series hair also existing as a physical LEGO part.
The images on Rufus McCallister need to be organized.