He was voiced by Zach Galifianakis, who also played Humpty Alexander Dumpty in DreamWorks' Puss in Boots.
In the opening of the film, the Joker and his men hijack a plane containing several tons of explosives, planning on using them to destroy Gotham City. When the pilot of the plane doesn't believe that Joker's plan will work, based on the fact that's he's tried to destroy Gotham dozens of times and has always been defeated by Batman, Joker informs him that his plan will work this time as he's had his minions take over the Gotham Nuclear Plant, plant a bomb powerful enough to destroy the city on to it and had Egghead cover the Bat-signal in eggs to prevent Batman from arriving.
With Joker and his minions threatening to destroy Gotham and Batman not being able to help, Commissioner Gordon and the GCPD are forced to surrender the Mayor of Gotham to Joker and his henchmen, however, unknown to them, the Mayor was actually Batman in disguise. As Batman begins to effortlessly pummel his minions, Joker begins to become frustrated as they're making him look bad in front of him. As Joker's bomb begins to reach the end of its countdown, his minions abandon the plant and Joker uses his balloons to try and evade Batman, however, he grabs Joker with his grappling hook and uses another hook to hold them in place. When Joker refers to himself as his greatest enemy, Batman shuts Joker down and tells him that he means absolutely nothing to him and that Superman is a better arch-nemesis, despite him not even being a villain. Batman eventually lets the heart broken Joker go in order to defuse the bomb.
While in his lair, a frustrated Joker laments to Harley Quinn about how Batman doesn't respect him as a villain and how incompetent his minions are, all while watching an interview between Superman and Lois Lane. When Superman talks about how he was forced to imprison General Zod inside the Phantom Zone, he also mentions how the Zone has some of the evilest villains of all time housed inside it.
During Commissioner Gordon's retirement party, Joker and his minions arrive and Joker orders Mr. Freeze and Clayface to bring him the new commissioner, Barbara Gordon, all while Harley Quinn changes into her civilian identity of Harleen Quinzel. However, Barbara fights off Joker's minions and confronts him at the same time as Batman and Joker reveals that he actually wants to be arrested and go to jail for his crimes, to the surprise of everyone, including his minions. While Batman is in complete denial of Joker's willingness to be imprisoned, he insists he is serious and traps all of his minions inside a giant present box..
With Joker and all of the other villains in jail, Batman sinks into a depression and spies on him and the other inmates, believing them to be up to something. At this point, Joker has Harleen drive up to Arkham Asylum with a van for "Phantom Zone Laundry" and Batman is inspired to put Joker in the Phantom Zone to keep him from committing crimes for good.
After stealing the Phantom Zone Projector from the Fortress of Solitude, Batman and his adopted son Dick Grayson try to sneak it into Arkham, but are caught and are forced to fight through Arkham's security in order to get to Joker's cell. Batman confronts Joker and sends him to the Phantom Zone, but is arrested and locked in a cell shortly afterward.
Joker then happily descends into the Phantom Zone and, after being scanned for how evil he is by the Zone's gatekeeper Phyllis, Joker meets the other prisoners of the Phantom Zone: Voldemort, Sauron, King Kong, The Wicked Witch of the West and her Flying Monkeys, The Daleks, the Velociraptors and Tyrannosaurus Rex from Jurassic Park, Agent Smith, Kraken, The Swamp Creature, Dracula, Medusa, Jaws, the Skeletons from Jason and the Argonauts and the Gremlins. Upon his arrival, the villains try to kill Joker, but he tells them all that he can get them out of the Phantom Zone and they agree to work for him in exchange. At that moment, Harley Quinn steals the Phantom Zone projector and sets it to release all of the villains entrapped in the zone. Upon doing this, Joker, as a giant face over the city, tells Gotham that he is going to take over the city with the help of real villains before unleashing them on the city.
Joker then has Sauron tell him the location of the Batcave and, after failing to realize that Bruce Wayne and Batman are the same person, he trashes the cave and converts Wayne Island into an amusement park. After Batman, Dick, Barbara Gordon and Alfred evade his attacks, destroy Sauron and crash land on Joker Island, Batman has the Scutler take his friends away from the island so he can stop Joker without endangering them. After being caught by Joker and his minions, Joker tries to get him to admit that he is his most hated enemy, but Batman refuses. Finally exasperated, Joker tells Batman that his only real greatest enemy is himself and banished Batman to the Phantom Zone. Joker and his minions then leave the Island and prepare to use Joker's bomb to destroy the city.
Upon being released with the promise that he will return all the escaped criminals, Batman teams up with Dick, Barbara, and Alfred, along with all the villains who escaped from Arkham to take down Joker and his minions. After the Phantom Zone villains are re-imprisoned and the city is blown up by the bomb, Batman convinces Joker to help him save the city by admitting that he truly is his greatest enemy, in a very cute declaration. Upon saving the city, Joker and Batman's villains walk away as Batman gives them a 30-minute head start.
The Joker is extremely boastful, destructive, violent, traitorous, manipulative, sometimes sarcastic, and arrogant. He despises his acolytes for their incompetence against Batman. He also showed that he was very wounded by Batman when he told him that in his eyes he was nothing. But near the end of the movie, Batman says that he's the reason he still fights crime in the city.
Unlike most depictions of Joker, this one is slightly more vulnerable and sensitive. He feels attached to Batman and is disappointed when Batman tells him that he doesn't see anything special in their relationship. Still, he is still extremely manipulative and intelligent, as he managed to make up a pretty simple but effective plan that included manipulating Batman. Most of the time, he is pretty polite to Batman despite their rivalry. He is shown surprisingly to not like too much violence, as when in the Phantom Zone, when the others said to eat him, he told them to cut down the violence, and when Sauron asked to make the city streets run red with Batman's blood, he disapproved of that.
The Joker has pale white skin, messy and spiky green hair, big eyebrows, wears red lipstick and has a mouth full of yellow shark-like teeth. He describes his body as "too much flab, not enough ab", implying that he may be chubby, though it's not visible since he is a standard LEGO minifigure. He usually wears an orange shirt, green tie with an orange skull pattern, purple striped vest with orange skull buttons, purple suit and purple bottom. He has heart and spades tattoos on his arms.
- The Joker is the first and only major villain of the LEGO Movie franchise who didn't completely redeem himself at the end of his movie. He is one of the two main villains that haven't redeem themselves (alongside Rex Dangervest).
- While he did help Batman save Gotham, he flat-out states that he and the Dark Knight were still very much arch enemies and that he had plans to commit more crimes in the future.
- He considers himself to be a foil for Batman, as he always has. The entire plot of the movie is basically driven by his hurt and outrage that Batman does not respect him as such.
- Out of all the Joker's incarnations, this is one of the rare few that isn't Pure Evil (unsurprising, since The LEGO Batman Movie was intended for younger audiences). Despite this, he has proven to be just as cunning and destructive (if not more so) as other incarnations, especially when fully driven.
- However, on that note, conversations about the Joker's past plans and schemes hint that all of those heinous actions were actually performed by him in the past and that he just goes through up and downs in his villainy's extremes.
- This version of the Joker is the only version of the Joker to have assembled such a large army of supervillains. It should be noted that, while it has many of Batman's more traditional foes, such as the Penguin, the Riddler, Bane, Catwoman, Killer Croc, Scarecrow, Poison Ivy, Two-Face and Mr. Freeze, Clayface and Harley Quinn, Joker's army is mostly composed of many of Batman's lesser-known villains. These being Calendar Man, Signalman, Kite Man, Killer Moth, Orca, Polka Dot Man, Crazy Quilt, the Eraser, King Tut, Magpie, Catman, Zebra-Man, and the Kabuki Twins (despite mainly being foes of other heroes, Clock King and Gentleman Ghost are also part of the Joker's army).
- His voice actor, Zach Galifianakis previously worked with Batman's voice actor Will Arnett in the 2009 live-action Disney film G-FORCE.
- Both the Joker and President Business help the protagonists near the end of their respective movies.
- Lord Garmadon pretends to help Lloyd but he ends up turning back to his own antagonistic actions.