Unlike Hafifu, Majinuni a slightly slimmer yet still bulky young ape with grey fur all over his body, and darker grey fur rimming the bottom half of his chest, limbs, and bangs. His head has a large tuft of fur/bangs which move across to the left of his face. His face, chest, ears, hands, and feet are beige. He also has two large pinkish-tan nostrils. His eyes are brown.
Majinuni has been described as 'buffoonish'. He is incredibly silly and immature, often making juvenile actions towards his brother, Hafifu. He does not recognize sarcasm and treats it as serious. Majinuni is particularly worried about disappointing his father, Sokwe, even going so far as to take up missions which he is not truly capable of completing in an attempt to please him. He wishes to feel like a prince just like Kion does, and is overjoyed (and often surprised) when he is praised.
Majinuni and his brother Hafifu locate some pangolins and enter a staredown. They start squeezing the animals under their armpits for fun, causing them to spray. Kion approaches the two foreign animals, and commands them to put down the pangolins. They are mildly confused by this due to how much fun they are having with them and continue squeezing them until Kion pins both of them down in fury, where they release the pangolins. After Hafifu comments that they don't know him, Majinuni asks him to let them go, and Kion tells them he will, but only on the condition that they leave the pangolins alone. They agree, and are let up.
Majinuni and Hafifu are happy when the rest of the Guard approach since it means more friends were brought there, but Kion is more interested in knowing why they are in the Pride Lands. They reply that they're looking for King 'Zimba'. The Lion Guard realize that they must mean king Simba, and Hafifu asks if they know him. Bunga explains how Kion is Simba's son. Majinuni questions if Kion is a lion whilst Hafifu questions if Kion is a prince before they both gleefully explain that they are too. They believe that they are the same as Kion and when questioned how Majinuni continues to explain how they have a message from their father to be delivered to Kion's father. Fuli drags Kion away, leaving Majinuni and Hafifu to pull faces at one another.
Hafifu then notices a 'stick', which is actually Ushari, who is slightly offended by the comment. They rush over to the cobra and Majinuni taunts his brother to get him to throw him at a baobab tree. Despite Ushari's protests, Hafifu lunges him towards the tree. Kion demands to know why Hafifu did such a thing, and he replies that he wanted to throw the stick. Kion explains that Ushari is not a stick, and Majinuni points out that sticks don't talk. Hafifu shrugs it off with a quick 'Kuishi Ni Kucheka'. Fuli asks what that is, and Hafifu tells her that it's their motto, which means 'to live is to laugh'. They start to sing, but Bunga and the Guard still have no idea about it. The gorillas are shocked that they've never heard about it, and then try to sing it in a different key, though Kion stops them and begins to guide them to his father.
At Pride Rock, Simba appears cognisant of their arrival. Every wet season, Sokwe sends a message to confirm whether or not he still agrees to the peace. He asks to see the two princes, and they arrive walking upside down. Bunga tries to introduce them, but Simba already knows them from Kion. He asks for the message, but they reveal that they forgot what it was (whilst blaming each other). Simba then tells his son that he and the Lion Guard will need to walk them home and receive the important message. Kion queries his father why they can't just get the message again but soon understands when the two gorillas are once again messing around, with Majinuni encouraging his brother to hop on one foot while patting his nose and rubbing his belly. Simba reveals that they live in the Theluji Mountains and that the gorilla princes should know the way. As Simba and Kion glance over, Majinuni decides to see who can balance the longest on no legs, causing them both to fall on their backsides.
The Lion Guard set out and approach the mountain base. Kion turns to Majinuni and Hafifu for further directions, but neither of them knows exactly where their home is, having only ever descended the mountain once, and never ascended it at all. Ono manages to scout out a path through the trees which they follow, with Fuli thanking them sardonically. Majinuni is surprised by her politeness, whilst Hafifu agrees that he didn't think they were helpful at all. After getting deeper into the jungle Kion peers around and asks them if anything looks familiar, but Bunga assumes that he was asking everyone. When Fuli explains that he was probably talking to the gorillas, the princes become scared, assuming that their father is nearby. When Kion confirms that he was referring to them, they are relieved. He asks them where to go, and they point the opposite direction. Beshte notices a chameleon and considers asking it, but the two gorillas chase after it for a game of 'chameleon hide and seek'.
Majinuni and Hafifu lose sight of the Guard. When Kion calls their names they respond, but admit that they can hear him, but not actually see him. Kion tells them to stand still and to keep responding to him when he shouts their names. Hafifu and Majinuni decide to turn it into a game, so that when Kion shouts 'Kuishi', they will respond with 'Ni Kucheka'. When Kion starts, they almost forget to reply. The Guard think they can hear them and wander off in one direction, but, instead of standing still, the two gorillas start to move about. Kion calls to them since the game isn't working and they change the game to 'forest hog chase'. Majinuni explains that they will snort like forest hogs while the Guard chase them. They start to run, whilst making noises.
Majinuni and Hafifu start to hear snorts in a foggy area, and they believe that the Guard are making the noises and enjoying the game too. However, they soon come face to face with an actual forest hog. Hafifu leaps into Majinuni's arms, who does not immediately see it for himself. When he does, he promptly drops his brother and the pair run away from it as fast as they can. The gorillas eventually slam into trees but, before the forest hog can attack them, Kion and the Lion Guard manage to get him to run away. Kion asks if they're okay, and even Majinuni is surprised that they weren't hurt. He mentions that Kion saved them, and Kion explains that it's what they do.
When it's suggested that they continue their journey, Majinuni suggests getting chased by the forest hog again. Beshte asks if there's anything wrong and the pair reluctantly confess that there is (whilst also assuring them that they really are as silly as they think they are). They explain that their father has never seen them as prince material, so they agreed to deliver the message to prove that he was wrong. However, since they forgot the message, they were worried about what he would say to them upon their return. Kion is understanding, since he never wants to let his own father down. He promises that when they start acting like a prince, they'll start feeling like one. Gathering their courage, the two gorillas agree to continue. Hafifu tries to get them to consider one more game, but the Guard refuse, and the gorillas continue.
The Lion Guard follow the two brothers over a cliff, and are inquisitive of the snow. The Guard have no knowledge of the substance, but start to explore it. Majinuni and Hafifu want to see the Lion Guard play with them. The Guard indeed start to join in, though Kion is cautious, remembering their mission. He finally exclaims Kuishi Ni Kucheka, and they have a brief respite to enjoy their newfound fun. After playing for a while, Kion comments that he could do it all day, but Majinuni reminds him of their mission. Kion wishes for one more look to remember it, but instead slips back and starts sliding down the snow. Bunga starts to run for him, but Majinuni halts him with his hand. Instead, he and Hafifu offer to save him since they know the mountains, and they start to slide down after the lion cub.
Majinuni and Hafifu slide down the same path, taunting each other as they do so. After sliding across trees, leaping into the air and sliding his behind against an ice wall, Majinuni reaches the end with his brother. Before they can rescue Kion, who is hanging onto the edge of a cliff, they bump into each other. Just as Kion falls, they reach down and save him. Kion thanks them for saving him, but Majinuni assures him that no thanks were needed since it was fun. Kion assures them that it was more than that, and that it was brave and prince material. The gorilla brothers are overjoyed to hear it.
The team finally reach their destination, where Sokwe is seemingly about to admonish his children for forgetting the important message, forgetting their way home and needing the Lion Guard's assistance. He then grabs two piles of snow and dumps it on their heads whilst proclaiming Kuishi Ni Kucheka. He laughs and his children join in. Sokwe informs them that Kion told him of how he was saved by them, and that he is proud of them both, true gorilla princes. While the princes smile, Kion reminds their father that they still need to get the message back his own father. Sokwe then notices Bunga's souvenir of a snowball, claiming it to be 'perfect'.