Sir Brrr, better known as the Cowardly Lion, is a major character in The Wicked Years, being the main protagonist in book three: A Lion Among Men.
A lion cub is brought into Shiz University by Doctor Nikidik for the purpose of studying the difference between animals and Animals. He says he named “Brrr” because it shivers often. Elphaba is outraged that he would use a defenceless cub for experiments, and the commotion causes the experiment to be put off and the cub's fate after that is unknown to her.
At the Mauntery, Brrr and his pet, a Glass Cat named Grimalkin (Malky) that he has named “Shadowpuppet”, arrive looking for Yackle. The maunts claim she's deceased but Yackle rises from the crypt, still alive. Brrr and Yackle begin a game of wits: he demands information on Madame Morrible and in exchange he'll tell Yackle about himself, his backstory.
Brrr doesn't remember his parents or where he was born, however, he grew up alone in the Great Gillikin Forest, learning language from the hunters that travel through his forest. One day he meets a soldier named Jemmsy, who had been caught in his own trap. Jemmsy implores Brrr to go to Tenniken and get help. Instead, out of fear and the naive belief that since this is the first person he's conversed with, Jemmsy's a friend, Brrr stays with the hunter until he dies. Brrr later claims the books that lay beside the hunter and takes Jemmsy's medal for courage to give to the latter's relatives. Thus begins the Brrr's unhappy personage as a “coward”.
After Jemmsy dies, Brrr goes out to find Tenniken. Not long after he started his journey, Brrr finds a terrified Bear cub. The Bear soon reveals that his name's Cubbins, and takes Brrr to his family: the Northern Bears under the rule of Queen Ursaless. She tells Brrr that to get to Tenniken, he must travel through the Cloud Swamp, a wet land inhabited by the Ozmists (ghost-like beings). Brrr and Cubbins have an "all but fatal" interview with the Ozmists. Brrr soon leaves Cubbins with the pile of books and he leaves the Great Gillikin Forest for the first time in his life.
When Brrr first ventures out of the forest, he finds out he isn't in Tenniken, but in Traum, a market town east of Tenniken. Brrr soon finds himself involved in a massacre of Glikkun trolls. Not knowing what to do, Brrr tells some of the trolls to play dead, as he thinks that it's the only way to bypass the slaughter, but they take his advice too late and become captured. The people of Traum celebrate the Lion for refusing to help their enemies, the Glikkuns, and Brrr safely gets out of Traum by train. While on the train, however, Brrr decides that his refusal to help the Glikkuns is really a badge of shame, and knowing that in Tenniken his reputation will precede him, he ultimately can't bring himself to go there, instead arriving in the University town of Shiz.
Brrr sets himself up in an apartment, and spends time in and around Shiz. The Lion soon finds a poem dedicated to humiliating him. Feeling embarrassed, Brrr packs up and leaves into the wilderness. Brrr wanders around the woods aimlessly for a while, until he finds a pride of Lions trying to make it in the forest. Brrr lives with the Lions for several years. But some of the Lions mock him, prompting him to once again, leave.
The next group that Brrr encounters is the Ghullim, a tribe of Ivory Tigers in the Wend Fallows. He hoped to pass right through their tribe without stopping, but they force him to stay with them for a while, if only to assess his status as a threat. While there, he befriends and ultimately falls in love with, Muhlama H'aekeem, princess and heir to the Chieftaincy of the Ghullim. But when they're discovered mating by Ivory Tiger scouts, her father Chief Uyodor H'aekeem announces that he suspects him of attempting to thwart his regime due to Muhlama being seriously wounded from the lovemaking, once again prompting him to leave, before they have his head for a trophy.
Within the following weeks, Brrr meets a strange group of travelers. One a little girl named Dorothy Gale, one a Scarecrow and the other was Nick Chopper, the Tin Woodman. Brrr decides to go with them to meet the Wizard of Oz. They soon find themselves on a quest to kill Elphaba Thropp, the Wicked Witch of the West. But Dorothy wants to reason with her instead. Once at Kiamo Ko, where Elphaba lives, she locks the Lion in a room with Liir. They soon break out in time for Elphaba to be vanquished. The five go back to the Wizard and get their rewards. All but Brrr got what they wanted (a terribly manufactured Badge of Courage, even more so than Jemmsy's). Brrr promises Dorothy that he'll protect and look after Liir, but Liir vanishes in the streets and crowds of the Emerald City. Brrr then goes off on his own path, like before.
The Lion has hit the outback again. With the other members of Dorothy's party laughing it up and having their own affairs, Brrr soon meets two old bachelors; Mister Mikko, an Ape, and Professor Lenx, a Boar. The three Animals discuss current events and past events. They soon rile Brrr up to retrieve money from the banks of Oz for them. The Lion soon becomes a broker for Animals, retrieving their money that is held in the banks since before they were forced to leave Oz. The forces of Oz soon discover that Brrr is bringing money into the Free State of Munchkinland and try him for being a collaborationist. He strikes a plea and is assigned by Avaric to go find the whereabouts of the Grimmerie, which leads him to his interview with Yackle.
Yackle tells Brrr that she awoke from a stupor already aged and having no memory of her prior life. It is later revealed she came from the Grimmerie and was created as a witness to the life of Elphaba Thropp.
Yackle admits to Brrr that she used to be a fake and had no actual powers, but after her first vision, induced by the Miracle Elixir, she began to have some powers of prophecy, which she used to keep track of Elphaba.
Later, when the Company of the Clock of the Time Dragon arrives at the mauntery, they bring the Grimmerie with it. The Clock reveals that Brrr's pet Shadowpuppet was actually a cat hired by the Wizard's government to spy on Elphaba and played a small role in Fiyero's death. The cat is ultimately imprisoned in the Grimmerie by Yackle, who in turn also reabsorbs herself into the book. After this, Brrr would leave with the company of the Clock of the Time Dragon, moments before the Emerald City attacks the mauntery.
Having joined with the company of the Clock of the Time Dragon, Brrr remains with them all through the novel. He enters into a “marriage” with Illianora and becomes a father figure to Rain. At the end of the novel, he becomes the Throne Minister of Oz, the first Animal to hold the position in a very long time (an event that Rain thinks Elphaba would be happy to see).