Codename: Kids Next Door: Operation Z.E.R.O. is the first movie to be made for the animated television series Codename: Kids Next Door. It originally aired on Friday, August 11, 2006 at 7:30 p.m. and aired on Cartoon Network as a made-for-TV movie.
The movie opens as Numbuh 1 is narrating, we then see massive factories covering the landscape of Britain and child labor widespread. All of this is controlled by an evil old man later known as Grandfather (though referred to as Pappy by his sons). However, one of his sons escapes a factory with his younger brother chasing him. The older brother climbs up a tree, while the younger brother climbs up to him telling him that he can't just run off in the middle of his shift and that "Pappy" will be angry not finding them.
But the older brother decides just to let him, stating that they've been slaving away making tapioca for 11,000 days straight, and their father does in sneer at them like he's the evil king of the world (which the little brother emphasizes that he is). The big brother states that he's tired of it and just wishes that they could fight back as he kicks the tree.
His wish is granted when he opens a door and stumbles on to a strange chamber, which contains 2x4 Technology as well as the Book of KND, a legendary book that contains instructions on how to use said technology as well as information recorded by previous KND operatives.
One of the sons plans to use these resources to rebel against Grandfather while the other balks and runs away, stating that they have "zero" chance of defeating their father. The son who stays dons sunglasses similar to Numbuh 1's, declares that he'll show him "what the number zero can do," and leads a revolt, destroying the tapioca factories.
However, Grandfather finds out about his rebellion and gives him three seconds to go to his room, or else. With his fists swirling with energy, Grandfather counts down malevolently. But once he reaches one, his son shouts his number and fires a beam at his father, decommissioning him and reverting him to a harmless old man.
This leads to the "Seventh Age of the KND" with Numbuh 0 becoming the greatest KND operative of all time. However, as so much time has passed, many regard the story as mere make-believe, though Numbuh One believes the story to be true.
The scene suddenly cuts to the present with Numbuh 1 telling the story, claiming that if he ever found the Book of KND, he would write only five words: "I am Kids Next Door".
He is then given an order by Numbuh 86 to deliver to the Kids Next Door Seriously Cool Museum of Artifacts and Stuff, a shrine to Numbuh 0 complete with the Recommissioning Module, a device capable of restoring decommissioned agents' memories.
Much to Numbuh 1's frustration, his important delivery turns out to be an ice cream cone for its tour guide, Numbuh 101, who is an ultimate fan of Sector V and regularly breaks into Numbuh 1's room.
As Numbuh 1 leaves, Numbuh 101 leads the new KND members through the museum. Midway into the tour, a coalition of KND villains suddenly attack the KND Museum while Stickybeard and his crew attack the Kids Next Door Moonbase.
Sector V then gets ultra alerts from both the Museum and the Moonbase. Numbuh 1 disregards the latter, believing that Numbuh 86 is sending him on another ice cream delivery, heading back to the museum to save it.
Just as they start fighting the villains off, they suddenly retreat back to the "convention center". Sector V then leaves also, which Numbuh 101 tries to look for a red marker to get their autographs. Unknown to everyone, the Recommissioning Module is missing.
Sector V then returns to space, just as the Moonbase is going critical. Numbuh 1 asked Numbuh 362 if they still have pretzel making capabilities, which is confirmed, he makes a daring plan. As his team sets the S.C.A.M.P.E.R.-S.O.O.P.R.E.M.E. to self-destruct on a collision course to Stickybeard's flagship, the Sweet Victory, drawing all pirate ships to defend him, only to divert to the moonbase, where they blow a hole in its wall and gather a ton of pretzels. Numbuh 1 then sends the ship right into the Sweet Victory's cannon, where is spews salt all over the fleet, forcing them to retreat.
As the KND repair their Moonbase, Numbuh 1 was scolded by Numbuh 362 for disobeying orders and responding to the Museum first. Numbuh 1 asserts that the museum is a priority, as it is a monument to Numbuh 0. Numbuh 362 snapped when the attack was a diversion, set by a single supervillain who coordinated all their enemies to attack them simultaneously. He only got lucky and since he is so hot headed and acts alone, she gives away his promotion to Global Tactical Officer to Numbuh 86.
Then, Numbuh 101 calls to say that he failed to get an autograph, before mentioning the stolen Recommissioning Module, which he considers damaged; Numbuh 86 nervously agrees, but Numbuhs 1 and 362 can tells she is hiding something. Numbuh 86 confesses that the Module is repaired, which she used to recommission Sector V after Numbuh 274 turned traitor (from Operation: E.N.D.).
Numbuh 1 then goes to retrieve the Module from the villains (despite Numbuh 362 and his team's warnings), but falls into a trap. Cree captures Numbuh 1 and, the rest of Sector V is captured by Chad. Father using one of his boogers to activate the Module, restores the memories of his father, who turns out to be the infamous Grandfather himself, making Number One believe that he is responsible.
Grandfather quickly usurps Father's position as leader of the KND villains, by calling Father a failure and telling him to leave stating that he only brought him back because he can't defeat the KND by himself.
Grandfather tells the villains that he will turn everyone who has ever been a kid into a Senior Citi-Zombie and make him mountains of tapioca to refuel him. While at first excited, the villains realize they were kids some point in their lives and try to run away.
Grandfather transforms the Toiletnator by holding him with his touch. He infects Mr. Boss and Crazy Old Cat Lady, and quickly, Knightbrace is transformed by Mr. Boss while Grandfather transforms all the villains at the Convention Base except for Chad Dickson (Numbuh 274) who manages soon to escape.
Cree flies into Grandfather, and becomes a Senior Citi-Zombie. Numbuh 1 gives up, frustrated at himself that he ruined everything and leaves himself behind, while Numbuh 5 is transformed by Cree trying to protect her comrades.
Soon, Grandfather with his slave army transform a KND Treehouse into a giant Tapioca-Factory where the Senior Citi-Zombie slaves making tapioca pudding for him.
Grandfather spreads this to every continent globally, turns the world's population of children into slaves, and transforms two thirds of the Kids Next Door treehouses into tapioca factories in only one hour.
At the Moonbase, realizing the severity of the situation, Numbuh 2 tells Numbuhs 362, Numbuh 86, Numbuh 3, and Numbuh 4 he has a device at Sector V Treehouse that can help build new Age-o-tonic Birthday Suits that protect them from the Senior Citi-Zombification. Numbuh 3 volunteers herself and Numbuh 4 to get it at the treehouse, meeting up with Tommy Gilligan, who was later turned into a Citi-Zombie by Toiletnator.
While avoiding a zombified Numbuh 5, Numbuh 3 is transformed as well. She tells Numbuh 4 to kiss her in a dark room and manages to transform him through a kiss. As the KND transform one by one, Numbuh 1 quickly becomes hard-pressed to survive as the last active KND member. But with some encouragement from Numbuh 101, Numbuh 1 got up on his feet and decided to track down Numbuh 0, their last chance of hope.
Back at Moonbase which is now under attack by Grandfather's Citi-Zombies, Numbuh 362, Numbuh 86, and Numbuh 2 try to contact Numbuh 3 and 4, only to find out they were transformed as well. Numbuh 362 orders Numbuh 2 to fix the Birthday Suits without his device and told Numbuh 86 to guard while she fights off with a Citi-Zombie Numbuh 60. Unfortunately, she is infected.
Once Numbuh 2 and Numbuh 86 are zombified, Numbuh 362 declares the KND destroyed. As the villains cheer, Grandfather roars that it is not the time to celebrate.
The villains point out that he defeated the KND, controls all the world's villains and he has all the tapioca he can eat; Grandfather pushes this off, stating that he must destroy the only thing that could oppose him: the Book of KND before his reign will be permanent. When kids read it, they discover the only thing more powerful than even Grandfather: hope. Grandfather swears that this time, he will destroy the book utterly.
Meanwhile, Numbuh 1 begins to track down Numbuh 0 in hopes of recommissioning him with KND Tracker, finally tracking Numbuh 0 to his very own home, and comes to the shocking realization that his father is Numbuh 0. After entering the Treasure Chamber of Coolness, Numbuh 1 recommissions Numbuh 0 and informs him about Grandfather's plans and the status of the entire world.
On the move to find allies, Numbuh 0 takes Numbuh 1 to Father's house, where it is revealed that Father is Numbuh 0's brother, making Father Numbuh 1's uncle and Grandfather his actual grandfather. It is also revealed, through the use of the Recommissioning Module, that the Delightful Children from Down the Lane are actually the long-lost Sector Z (the numbuhs 0.1, 0.2, 0.3, 0.4 and 0.5), who were kidnapped and permanently brainwashed in a "delightfulization" experiment gone right.
The Module restores their memories, but will only have a temporary effect (about an hour). Numbuh 1 and Sector Z make their way to the Moonbase while Numbuh 0 and Father stay behind to face Grandfather. Grandfather is glad to see his eldest son but looked down on the other, who attempts to asserts that he's more evil than his brother, only to be blasted by Grandfather.
Father then gets angry, recreating his black suit but then chickens out again, leaving Numbuh 0 to deal with Grandfather. Grandfather demands that his son behave for once and asks for him to fetch him the Book of KND; Numbuh 0 refuses to budge. Enraged, Grandfather declares that the only mistake he made was giving his own son a choice and engages his son, slowly agifying him.
On the Moonbase, Numbuh 1 and Sector Z manage to defeat the zombified Sector V,, and maneuver the moon to face Earth. Unfortunately, Sector Z revert back to their evil selves and attack Numbuh 1. On Earth, Grandfather acknowledges Numbuh 0's impressive resistance but states that he can't stand against him forever; he stands "zero" of a chance; Numbuh 0 acknowledges this, also stating that his son is Numbuh 1.
At that moment, Numbuh 1 manages to defeat the DCFDTL, sending them to space in a escape pod, but not before the targeting system is destroyed. Numbuh 1 switches to manual targeting, but it requires four other members to operate.
Fortunately, Numbuh 2's suits are able to partially reverse Grandfather's aging effects, and Sector V uses the weapon to literally drop the entire Moonbase on top of Grandfather, just as he found the Book of KND in Numbuh 0's back pocket.
Grandfather survives the giant impact, but is lured into the Decommissioning Chamber by Numbuh 0, which results in the both of them getting their memories erased. With Grandfather defeated, the world turns back to normal as the Senior Citi-Zombies transform back into their normal, harmless selves.
However, when Numbuh 1 attempts to Recommission Numbuh 0 once again, it immediately falls apart. He comes across a recorded message from Numbuh 0 telling him that he has destroyed the Recommissioning Module and that he would rather not have his memories restored so that he could complete his greatest mission of all: being a good father to his son. He declares Numbuh 1 keeper of the book and advises him to write new stories in it.
One month later, the existence of Numbuh 0 is public knowledge and considered fact. The Moonbase has been completely rebuilt and is larger and better than the previous one. It also now contains a massive statue honoring Numbuh 0. Numbuh 1, who now has possession of the Book of KND, writes his entry into the book. The entry consists of only five words: "We are Kids Next Door." The movie ends with Numbuh 1 revealing the entire (presumably) KND around him.
- Dee Bradley Baker - Numbuh 4/Wally Beatles, Mr. Fibb, Toilenator, Joaquin, Tommy Gilligan, Delightful Children from Down the Lane member, Additional Voices
- Benjamin Diskin - Numbuh 1/Nigel Uno, Numbuh 2/Hoagie P. Gilligan Jr., Numbuh 101/Matthew, Delightful Children from Down the Lane member
- Cree Summer - Numbuh 5/Abigail 'Abby' Lincoln, Cree Lincoln, Delightful Children from Down the Lane member
- Lauren Tom - Numbuh 3/Kuki Sanban
- Ogie Banks - Sector Z Numbuh 0.1/Bruce
- Jeff Bennett - Mr. Boss, Mr. Fizz, Benedict Wigglestein
- Grey DeLisle - Crazy Old Cat Lady, Gramma Stuffum
- Cam Clarke - additional voices
- Jennifer Hale - Numbuh 86/Francine 'Fanny' Fulbright, Numbuh 363/Harvey McKenzie, Computer
- Mark Hamill - Stickybeard
- Jason Harris Katz - Chad Dickson
- Janice Kawaye - Numbuh 83/Sonya, Numbuh 84/Lee
- Tom Kenny - Knightbrace, Chester, Mr. Wink, Sector Z Numbuh 0.2/David, Additional Voices
- Maurice LaMarche - Father/Benedict "Ben" Uno
- Matt Levin - Numbuh 60/Patton Drilovsky
- Rachael MacFarlane - Numbuh 362/Rachael T. McKenzie, Sector Z Numbuh 0.3/Ashley
- Candi Milo - Additional Voices
- Daran Norris - Count Spankulot, Janitor
- Neil Ross - Grandfather
- Frank Welker - Monty Uno
- Dave Wittenberg - Young Monty Uno/Numbuh Zero, Sector Z Numbuh 0.4/Lenny