When a rare pink and glitter-filled moment of fate makes Thelma the Pony's wish of being a unicorn come true, she rises to instant international pop-superstar stardom, but at an unexpected cost.
Thelma dreams of being a glamorous unicorn. Then in a rare pink and glitter-filled moment of fate, Thelma's wish comes true. She rises to instant international stardom, but at an unexpected cost. After a while, Thelma realizes that she was happier as her ordinary, sparkle-free self. So she ditches her horn, scrubs off her sparkles, and returns home, where her best friend is waiting for her with a hug.
Thelma (Brittany Howard) is a small farm pony (whose main job is to discard manure from the farm) who dreams of becoming a famous musician alongside her band mates Otis the donkey (Will Forte) and Reggie the llama (Jon Heder), who form a band called The Rusty Buckets. Thelma dreams of fame and adulation from the audience and stage diving into the crowd. Reggie believes that they need to use Pyrotechnics to impress the judges at their upcoming audition. Thelma and the band have been chasing their 15 minutes of fame for 10 years.Nikki Narwhal is the reigning music sensation. Thelma believes Nikki has it all and she gets to sing at SparklaPalooza every year.Zirconia (Shondrella Avery) is a stallion at the farm, who makes fun of Thelma's ambition. Zirconia says that only her own troupe has the looks and the talent to make it big.
Thelma humiliates herself at an audition that would have guaranteed them a spot in the singing showcase event SparklePalooza. Thelma and her band went right after Zirconia who scored a perfect 10. Thelma and her band are not even allowed to perform on stage as the judges say that the band has no sparkle or appeal for the audience. Thelma tries to confront the judges but ends up tripping and the whole equipment falls on her.Otis tries to cheer Thelma by playing Dungeons and Dragons. Thelma wants to be a Unicorn character, but Otis says that it's a level 300 character and hence Thelma cannot be her, depressing her further.
At work the next day, Thelma finds a carrot on the ground and sticks it on her forehead with mud.Later, a clumsy truck driver Crusty Trucker (Zach Galifianakis) accidentally drenches Thelma, while wearing a carrot on her forehead, in glitter and pink paint, giving her the appearance of a unicorn. Her appearance attracts a small crowd to her farm, and she seizes this opportunity to sing in front of them. Thelma claims to her audience that singing is her superpower, as every Unicorn is supposed to have one. Despite Otis' objections of lying to people in favor of performing as their true selves, Thelma decides to stick with her facade. She doesn't wash off her Unicorn makeup after the crowds have left.The video of her performance makes it to social media, giving Thelma worldwide recognition and adulation, like she always wanted.
A blind retired record dealer named Peggy Purvis (Maliaka Mitchell), after hearing The Rusty Buckets on TV, decides to make them her new comeback attraction. Peggy wants to record an album with The Rusty Buckets. Peggy is blind and so does not care what Thelma looks like. She asks Thelma to sing true and from the heart.Soon, Thelma gains the attention of a snooty manager named Vic Diamond (Jemaine Clement), who works for the arrogant singer, Nikki Narwhal (Ally Dixon). Nikki's concerts have been getting bad reviews lately, and Vic is looking for a new and fresh act.Vic contacts Peggy and after some arm-twisting, convinces her to make Thelma an opening attraction at Nikki's new concert. Reluctantly, Peggy agrees and are picked up by Vic in Nikki's private jet. At the destination, Vic separates Thelma from the rest of her entourage, and they travel in separate limos. Vic then uses a missile to destroy a limo carrying Peggy, her husband Gerald (Jared Hess), Otis and Reggie while he and Thelma go on without them.
At Nikki's show, when her friends fail to make it in time, Thelma is forced to sing solo, where she receives a standing ovation from the crowd. Vic makes her sign a contract to make him her manager, which also allows him to leave Nikki. Outraged over being upstaged, Nikki attempts to attack Thelma, but is booed by the audience, causing her fame to plummet.
Outside while walking through a crowd of fans, Thelma meets Otis and the two have an argument about him and the rest of her friends' not being at the show. Thelma reveals her secret to Vic, but he doesn't care, claiming that putting on a facade is the only way to succeed in the industry. Vic convinces Thelma to pretend dating internet star Danny Stallion (Fred Armisen) (who got famous for his chewing Cud videos that got over a billion views) to increase her fame. Meanwhile, Nikki orders her assistant, Megan Shank (Edi Patterson), to find some dirt on Thelma in order to ruin her image.Meanwhile Vic makes an album of Danny and Thelma with a song on Cud, written by Vic's AI lyrics writer Bridget. Vic also launches a number of products under Thelma and Danny's brand name, including cereals and cologne. The album hits #1 on the charts.Thelma finds that Otis and Reggie found a new singer for their band.
Eventually, Vic manages to book Thelma a spot on SparklePalooza. However, during an awards ceremony in which Thelma is attending, Megan, after discovering her "horn" coming loose (after having her minions attack Thelma with eggs which budges the horn loose).Megan confronts Thelma in the bathroom, washes off her unicorn disguise and threatens to reveal her deception unless she permanently quits the music business. Reluctantly, Thelma agrees and leaves, causing her to be declared as missing as a result.
Two weeks later, Thelma hitches a ride with the driver who instigated her unicorn disguise and reveals that he's been hiding a secret from his girlfriend, as he feels that she wouldn't accept him for who he is. Inspired, Thelma tells the driver to drop her off at a gas station where she reunites with her friends.
Wanting to fix things, Thelma and her friends go to SparklePalooza just as Nikki is about to go on. After evading Nikki and Megan, Thelma dons her unicorn persona and proceeds to reveal her true self by wiping off her disguise. Although outraged at first, the crowd soon accepts Thelma for who she is when she and her friends play a song about embracing one's true self. Touched by her performance, a reformed Nikki rejects both Megan and Vic as her clients.
Sometime later, Thelma and her friends are still in the music business, now under a record deal made by Peggy. Suddenly, the driver arrives and accidentally drenches Otis in white paint and feathers, giving him the appearance of a Pegasus making Thelma burst out with laughter.
