King Julien is an eccentric, conceited, and sometimes insane lemur who, despite his title, holds no actual authority - his title being merely a self-proclaimed one. In nearly all mediums, Julien is shown to be vain and self-centered, glorifying himself despite his lack of achievements as a ruler. However, Julien is also a keen dancer, as was shown in his debut appearance in Madagascar and its subsequent sequels.
In all appearances, Julien is assisted by his advisor, Maurice, an aye-aye lemur who - despite his occasional frustrations with Julien - remains Julien's faithful and (only) friend. Julien is also the subject of worship by Mort, a mouse lemur whom Julien treats with disgust for being so annoying.
- Main article: Madagascar
Julien debuted along with the other characters of the franchise in the 2005 film Madagascar. In this film, Julien has proclaimed himself king of the lemurs, but his authority remains unquestioned, with his lemur subjects gladly participating in Julien's parties.
Despite initial skepticism from Maurice, Julien decides that Alex (Ben Stiller) should protect the lemurs from the Foosa who are constantly attacking the lemurs. Julien's idea briefly falters after Alex's taste for red meat resurfaces, but after Alex chases the Foosa away in a fit of rage, and his appetite for red meat is cured by the penguins, Julien celebrates the defeat of the Foosa.
Madagascar: Escape 2 Africa
- Main article: Madagascar: Escape 2 Africa
In the sequel, Julien decides to travel with the main characters back to New York City, on the grounds that the plane they are using is his property. Whilst in flight, Julien and Maurice occupy the First Class cabin of the plane, and exhaust Private (who is posing as a steward) with their demands.
During a crash-land into a wildlife reserve in mainland Africa, Julien is sucked out of a hole in the plane, and lands safely. He quickly attempts a non-hostile takeover of the reserve, but is only able to convince a group of flamingoes and ostriches to obey him. He later attempts to perform a sacrifice to a nearby volcano, which does not go according to plan.
The Penguins of Madagascar
- Main article: The Penguins of Madagascar
In the television series The Penguins of Madagascar, Julien is the resident lemur at Central Park Zoo, with Maurice and Mort as his penmates and followers. The other zoo animals do not question Julien's claim as ruler of the zoo - Skipper even acknowledges this openly in the episode Kingdom Come - although his proclamations and decrees are generally ignored.
Julien's arrogance and selfishness became even more apparent in the television series, where Julien wastes time gloating over his noble features rather than take responsibility. For example, in Operation Plush and Cover, he wastes his time complaining about the poor quality of toys made in his likeness rather than aid the penguins on their misison, whilst in Crown Fools, he raises the ire of Marlene by trying several new crowns she gave him after his old one fell in a sewer, whilst he had a spare crown all along.
The animated series also began a rivalry between Skipper and King Julien, particularly as Skipper is usually the first to react to Julien's incessant gloating, as was the case in episodes such as Penguiner Takes All and Operation: Plush and Cover. A similar rivalry in the series - albeit to a lesser extent - also emerged in later episodes between Julien and Joey (an antisocial kangaroo) for the exact same reasons.
- Main article: Merry Madagascar
King Julien returns in the 2009 midquel Merry Madagascar (again voiced by Jacobs), in which he celebrates Julianuary, a form of Christmas dedicated solely to him. He also fears the "Big Red Night Goblin" (i.e. Santa), who pelts coal at him for being naughty. In the film, Santa teaches Julien the gift of giving rather than receiving, and thus Julien learns the true meaning of Christmas.
- Main article: Madagascar 3
Julien has been confirmed to appear in Madagascar 3, although his role in the film has not yet been made clear.