Basi is the largest hippo in his pod. As a hippo, he is massively portly and well-built. He has hairs on his muzzle and notices in his ears. He has dark brownish-gray skin, a pale underbelly, dark spots on his back, and dark rims around his eyes.
Much like his son, Basi is a gentle giant with a sunny disposition. Basi is amicable and open, willing to engage in conversation and negotiate according to the customs of his homeland.
Being so learned in the ways of the animals, Basi is knowledgeable and wise. Despite being an animal with a very different way of life, he understands the customs of the crocodiles and how this affects his pod's everyday life.
Basi is first seen when Beshte brings his friends to Big Springs. While there, Beshte explains to them how the fish pick his hide and teeth clean, and Basi adds that the crocodiles eat the fish when the population spikes, thus fulfilling the Circle of Life.
In the midst of their talk, Pua, the leader of the crocodiles, approaches and asks Basi how the fish are faring. Basi suggests that the float come back next week, and Pua amicably agrees, leading his crocodiles away. However, before he can leave, he is challenged by Makuu, who accuses him of being afraid of Basi. The two arrange a mashindano, which Basi explains as being a physical contest that determines the leader of the crocodiles.
When the mashindano takes place, Basi watches alongside his son, Beshte. At the start of the event, Basi can be seen chanting, and in the midst of the brawl, he comments that Pua is too tired and weak to take on Makuu. Not long after this comment, Makuu wins, and Basi explains that as defeated leader, Pua is banished from the crocodile float.
Basi makes his final appearance when the Circle of Life is brought back into balance, with the crocodiles returning Big Springs to the hippopotamuses. As Makuu strides sullenly out of the water, Basi calls out after him, inviting him to come back once the fish are in plenty. He reminds him that all he has to do is ask, and Makuu promises to keep the proposition in mind.
Along with Mbuni and Twiga, Basi practices a song for the Kupatana celebration. Simba listens from a nearby hillside and warmly compliments Basi's performance to Beshte, who tells the king that Basi has been practicing relentlessly. At the official celebration, Basi contributes his voice to the opening choral piece, and he watches in awe as the baobab blossoms begin to bloom.
Basi and his son Beshte are in the Flood Plains, walking through the reeds and stomping them down. Basi explains to his son how making the Hippo Lanes after a big rainstorm has been a hippo tradition for a long time. He goes on to say that the lanes help others cross the Flood Plains, and that a good Hippo Lane must be "straight and true" and that someday, it will be Beshte's turn to make the lanes.
Suddenly, a voice calls out for help. The pair rush towards the sound of the voice and locate Young Rhino, who is trapped in the reeds. Nearby, Makuu and another crocodile are lurking, positive they won't find him in the mess. However, Beshte bursts through the reeds, and warns him to back off, reminding him that the Flood Plains are a safe spot after a rain storm. Makuu challenges Beshte, believing him to be outnumbered. Basi soon arrives and chastises him, and Makuu slinks away, muttering angrily that hippos always follow the rules.
Confirming they're gone, Young Rhino explains how he was trying to cross when he became ensnarled in the reeds and mud. Basi comments that he should have waited, but Young Rhino claims that he was in a hurry, but soon admits that he should have waited. Basi and Beshte start to untangle him, but a flock of egrets startles him greatly, and he accidentally thrusts his horn against Basi's leg. Young Rhino is freed regardless, and he thanks them, promising that he'll wait. Basi assures him that it won't be long.
Basi with his son Beshte, Fuli, Ono, Bunga, Kion and Nala