Karl is a former self-proclaimed genius and an antagonist in the All Hail King Julien Netflix series.
He is a card-carrying villain (literally) who took it upon himself to become the arch-nemesis of King Julien. Known for his theatrics and love of over-complicated plans, Karl is the kind of villain who rather "arches" his nemesis than to actually kill him. It is revealed eventually that he blames Julien for the way he treated him in high school. He is always encountered with his pet hissing cockroach, Chauncey, who is actually his one true friend and companion as well. He tends to make dramatic getaways when thwarted, announcing "This is not over - not yet, at least."
After he did some attempts on King Julien's life where Mort took a blow to every attempt, Karl makes himself known to King Julien and invites him to his lair with the directs on the brochure. After Clover and Maurice are captured, King Julien makes his way to Karl's lair at a crashed zeppelin where Karl mentions his plans to raise the zeppelin and take over the world with King Julien as his partner. While Karl was ranting about his plans, King Julien manages to free Clover and Maurice. When King Julien, Clover, and Maurice exit the zeppelin, they are confronted by Karl who prepares to fire a laser at him until the balloon carrying the rocks with every wishes that the lemurs wrote on them for the Sky God member Frank falls from the sky and lands on Karl. Seeing his "Surprise Me" wish roll against him, King Julien took it as a sign that Frank had helped him defeat Karl.
In "One More Cup," it is revealed that Karl survived and returned where he hooked the whole kingdom on caffeine which was part of his plan. He states he watches King Julien fooling around in the Cove of Wonders instead of following his kingly duties. Karl threw a bag of coffee beans in the ocean and knew that Julien would find it because it has the word "king" on it. The hyper kingdom threw out King Julien, Maurice, and Clover. With the help of Mort (who became intelligent from the coffee), they plan to destroy Karl's coffee supply. They approach to Karl's zeppelin while Smart Mort walks through the fields where he meets jumping rats working there. Karl returns, finding them, and tries to destroy them when the jumping rats break through the door demanding a raise from their boss, even the ones cornering Julien, Maurice, and Clover. Later, Karl surrounds the group and prepares to fire his incinerator at Julien until Smart Mort bites him on the foot. King Julien has the weapon and sees that Karl has Mort in his clutches and says that he has one shot, him or Mort. Julien, having no choice, aims the incinerator at the fields destroying the crops leaving Karl devastated worrying what will Bruce will say when he returns from his vacation. King Julien now aims the laser at Karl who states that it charges. Karl escapes in a hot balloon with Chauncey driving it. Karl vows that he will return and will never stop getting rid of King Julien.
In "Are You There Frank? It's Me, Julien," Karl creates a special armor that allows him to pose as Frank the Sky God in order to get the Lemurs to oppose Frank's brother Larry the Volcano God by sacrificing King Julien. With help from Mort operating the Larry armor that Timo built, King Julien repels Karl. in "Revenge of the Prom", Karl reveals that he was in all of Julien's old high school classes, but Julien never noticed him.
In Season 5, it is revealed Karl's older and domineering brother Bruce has a successful coffee business, and he wants to partner with King Julien - but he ends up buying out Julien and spreading his coffee shops everywhere. Clover and Maurice ally with Karl, who hates his brother for bullying him, and together they ruin his company. At the end it is revealed this was Karl's plan all along, he knew King Julien would cause Bruce's downfall.
In "Karl Maggedon", Karl decides to retire and announces to leave his role as King Julien's arch-nemesis to whoever wins the contest - with Fairfax and Pancho, Tammy and Butterfish, The Crocodile Ambassador and the Crocodile Princess, Mort and his Grandpa, and King Julien and Clover contesting for the role (the latter figuring he can be his own nemesis). This all turns out to be a ruse, to keep Julien busy while Karl prepares his ultimate weapon, the Karl-Star to destroy Madagascar with lasers. However, at King Julien's signal, the lemurs use mirrors to make the Karl-Star blow itself up. Julien reveals he expected this from Karl as he always kept bragging about his penchant for using lasers. Defeated, Karl makes good on his promise to retire and travels to Florida with Chauncey on a hot air balloon, admitting that there are no "not yet, at leasts" this time.
In "The Return of the Revenge of King Goobot" Karl gives up villainy and helps King Julien save his kingdom from the clutches of the Yolkians. After King Goobot and Commander Sphnx's defeat. Karl decides to become a superhero and Ooblar becomes King of Yolkus.
In "Bye Bye Clover, Part 2" Karl and Chauncey make a cameo, singing "Thank You for Being a Friend" with Julien and the others.