Mwenzi is a medium built tickbird with brown feathers of various shades on his body. His wings and tail tips are the darkest brown, with his underbelly being the lightest. His talons are dark gray. His eyes are black and rimmed with yellow. His beak is red.
Mwenzi is a rather snappy and sensitive little bird, who has a tendency of hiding his true feelings when chafed. Even in a bad situation, he will try his hardest not to show fear. He is not one to hold a grudge and shows tremendous loyalty and bravery when his friend is in danger.
On their way to Tamasha, Kifaru the rhino blames Mwenzi for their tardiness. Angered, Mwenzi leaves Kifaru, and aimlessly flies around elsewhere.
When the Lion Guard track him down, he ignores Beshte's call and flits past them too fast for them to even see him properly. Instead of answering the hippo, he swoops down to take a sip from a nearby watering hole. When he hears a cry from a supposed "rhino" who is covered in ticks, he flies over to investigate, promising to help the rhino out after landing. He discovers that there are no ticks, and is surprised to see that the rhino is in fact Beshte. He exclaims that Beshte is not a rhino just before Bunga captures him, prompting a slightly confused Mwenzi to ask what the Lion Guard want with him. The Guard then inform him that Kifaru has been causing damage around the Pride Lands due to his poor eyesight and that he needs to return to him.
Mwenzi then informs them that the reason he left was because Kifaru was blaming him for being late to the Tamasha, even when it was his fault. He goes on to say that Kifaru always blames him for being late. Mwenzi flutters over to Fuli and asks her what she would have done in the same situation, and she admits that she would have left. Kion prompts her to add that it doesn't mean that he should leave Kifaru. Beshte then adds that Kifaru is lost without him, metaphorically speaking. Kion suggests that Mwenzi himself is not doing so well either, and the tickbird agrees that he's used to having a job. When Kion suggests that the job is usually looking after Kifaru, and after a bit of encouragement and being told that Kifaru misses him, he agrees to speak with him, adding that it can't hurt to talk.
The Lion Guard return Mwenzi to where Kifaru is being taken care of by Ono, who is cooling him off with his wings. However, since Mwenzi is so small, Kifaru confesses to the egret that 'little' Mwenzi couldn't do it even if he tried. Mwenzi then overhears Kifaru call Ono the best, and questions Kion on how lost Kifaru really is without him. Despite Kion trying to assure him that he was when they left him, Mwenzi swoops over to the rhino. Although Kifaru is overjoyed that Mwenzi is back, he merely states that it's to say goodbye forever before taking off. Despite distressed cries from Kifaru and Ono, the upset tickbird continues flying.
He eventually lands on a branch overlooking a lake. With a sorrowful look planted on his face, he rejects Ono's plea to leave the area, since Makuu and his float are usually hanging out there. But Mwenzi believes that Ono is trying to replace him since Kifaru seemed more than happy with him instead. The egret explains that he couldn't even get him to turn right, and questions him about how to make such a turn. Mwenzi questions him on why he should tell him, so Ono makes the assumption that he couldn't either, in turn causing Mwenzi to prove him wrong by answering the question. Ono then praises him for it, before asking about Kifaru's noises and how he handles it. Ono mimics the noises, and Mwenzi corrects him on how Kifaru really sounds, prompting the egret to laugh merrily.
Soon, Mwenzi starts to remember their friendship, admitting that Kifaru is his best friend. While the two start to speak about best friends, unbeknownst to them, Makuu surfaces nearby. Ono then suggests that Mwenzi try to rekindle their friendship, positive that they can patch things up. Mwenzi agrees to speak with Kifaru. But after Ono flies away, Makuu hits the branch of the tree, and Mwenzi is sent tumbling in the air. Hearing his call, Ono returns and manages to grab the tickbird with his talons and save him from the jaws of Makuu just in time. He places him on a higher branch, but Mwenzi's wing is injured. Ono leaves to get help, leaving Mwenzi to watch the croc from above.
Makuu starts pounding the tree violently with his tail, but Mwenzi does not fall. The tickbird tells Makuu to give up since he can't reach him and he won't fall, but Makuu tells him that he has a trick up his sleeve. He dives under and pounces up, breaking away a large portion of the tree branch, though not the segment where Mwenzi is perched. Mwenzi starts to breathe erratically, and Makuu assures him that he won't be so lucky next time. But just before he can strike again, Kifaru arrives to stop him. Although Mwenzi is overjoyed to see his friend, Kifaru is unable to see and rushes straight past him and crashes into a hollow tree stump. With his horn trapped, Makuu summons three members of his float, and they start to approach Kifaru, much to Mwenzi's dismay.
Soon, the Lion Guard arrive to help fight the crocodiles. But with Kifaru still struggling, Mwenzi plucks up the courage to leap down. He hops over to Kifaru and directs him with some simple instructions, and Kifaru manages to get the stump loose. Just as a crocodile tries to attack Mwenzi, Kifaru turns around at the sound of his friend's worried cry, knocking him away. He apologizes, but Mwenzi encourages him to keep going. Kifaru then charges ahead, knocking the crocodiles away from the struggling Lion Guard members, before finally knocking their leader Makuu away.
With the crocodiles leaving the watering hole, Kion expresses his gratitude to the rhino. Kifaru then passes the credit to his tickbird, who passes it back to him. The two then share a brief song together, nuzzling at the end. Kifaru then turns to Ono, informing him that he can no longer be his tickbird and that he hopes he won't be too upset. Though Ono isn't bothered at all by his words, and offers him a relieved smile.
The Lion Guard then join Kifaru and Mwenzi at the Tamasha. When Kifaru cheers the wrong way, Mwenzi whispers into his ear for him to face the correct way, where two rhinos are engaged in a friendly spar. Another tickbird comments that he didn't expect to see him there and that he had heard they had split up. The friends deny such a thing and enjoy the show.