Mbuni bears black and white feathers, a long, pale pinkish white neck, and dull grayish pink legs. She has large, round blue eyes (brown in some episodes) and a small fringe of white feathers atop her head, as well as a few speckles on her neck.
Mbuni is shown to be very friendly, empathetic, compassionate, cheerful, and calm at most times. She is quick to take advice despite how poor it may seem, and has confessed to being afraid of hyenas. When frightened, she will run in any manner of direction until she finds some sort of solace. Mbuni is also incredibly respectful for her King, Simba, and will bow whenever she is in his presence.
Mbuni seeks the council of Bunga the Wise, listening to his song whilst waiting in line. When she finally meets Bunga, he tells her to stick her head in the ground to avoid seeing hyenas. She is later rescued by the Lion Guard after getting her head stuck in a hole, where she explains what she was doing to the Guard. She also mentions that she was following Bunga's advice.
Mbuni is seen rehearsing a song for Kupatana, though she is stopped by Zazu after accidentally mispronouncing her words. Later, she is seen grazing peacefully in the Pride Lands as Beshte and Bunga are on patrol, confirming her excitement at the upcoming Kupatana event that is taking place later that evening. She is seen later still at the Kupatana Celebration that evening, participating in the song and enjoying the event.
Mbuni is first seen giving Bunga a ride on her back during (When You're) Running with the King. She and her herd are later seen running around erratically near a cliff edge. Ono sees that this is due to a mudslide which is slipping down and will eventually catch onto their eggs, sending them over the side of the cliff. With Simba temporarily in charge of the Lion Guard, he tries to stop the eggs from being swept away by placing a log in their path. But due to his lack of skills working with a group, he inadvertently causes Beshte to crash into the log. After a struggle, the Lion Guard are able to prevent the log from smashing into the eggs whilst also saving them from being swept away. The final egg is saved by Simba, who Mbuni and her friends bow to with their thanks, honored to have had their eggs saved by the king.
Later, Swala's Herd stampede towards Mbuni and the other ostriches' nest after being startled by Simba's fast approach. Ono reports this to the Guard and, after arrangements are made, Fuli approaches the ostriches and tries to calm them down. When her soft voice fails to stop them from running about, she shouts for them to stop, which gains their attention. Shortly after Fuli calms them down, Ono calms down the gazelles, saving the ostrich eggs from being smashed for the second time that day.