Operation: KID NINJAS' COMEBACK is a Series One Fanfic.
Team and Destructively Nefarious Kids episode
Villains: Delightful Children, Dastardly Duo from the Left Tunnel
Ally Debuts: Kid Ninjas from the Dojo
KND Technology used: SCAMPER, SPLANKER
DNK Technology used: MOMSTER, HORNETT
Villains Technology used: DDFTLT Secret Weapon
Not Another KND!
The Fanfic starts with the Sector V team flying across the ocean in the S.C.A.M.P.E.R. The Destructively Nefarious Kids flying in their M.O.M.S.T.E.R. vehicle, are not far behind. Negative Numbuh One calls the KND on the S.C.A.M.P.E.R.'s communication system to ask what they're looking for. Numbuh One tells them of another, much older branch of KND that existed even before the name "Kids Next Door" did. These kids were called the "Kid Ninjas from the Dojo".
Not Another Island!!
The KND and DNK land on an unknown island. Despite its absence on Numbuh Five's computer map, Numbuh One claims it is the Kid Ninjas from the Dojo's island and, sure enough, the Dojo can be seen hidden in a clump of bushes when he says this. Numbuh 4 stumbles upon a hidden lever (a tree branch stuck in the ground) which opens the bolted-shut door of the Dojo, allowing the KND to enter. Negative Numbuh 1 calls to them to say that he and his team will be waiting for them outside.
The Trouble with Tunnels
As the KND wander the labyrinthine tunnels of the Dojo, a pair of eyes watch them from the shadows. The team enters a hidden room, only to find that it's rigged, with bolt-tipped arrows and stones flung from slingshots high overhead. While Numbuhs 2, 3, 4, and 5 manage to escape, Numbuh One is not so lucky, as he gets hit in the back of the head with a stone and conks out. When he awakens, he is in what could easily be a primitive version of the Med Lab in the KND treehouse. He tries to sit up, but a firm hand holds him back. A pair of boys dressed as ninjas stand over him. They introduce themselves as the legendary Kid Ninjas, each of whom is named for a different letter from the Greek alphabet, though the Kid Ninjas use the same "numbuh-ing system" that the Kids Next Door use. While Numbuhs Alpha and Beta attend to Numbuh 1, Numbuh Delta (who is a girl) hurries to fetch some ointment for One's forehead.
Meanwhile, the Delightful Children from Down the Lane are also searching the Dojo. Apparently, they used the R.R.I.D.M. to reach the island, but the Machine wasn't large enough to fit inside the Dojo so they left it outside. The DCFDTL almost stumble upon the same room as the KND did, but the activation of a unseen lever causes the door to swing down in their faces. The Delightfuls question who did that, and we see the "culprits": a pair of teenagers who are dressed in black-and-red ninja dress (as opposed to the Kid Ninjas' white and gray attire), similar to how the Teen Ninjas' Battle Ready Armor looks. The pair introduce themselves as the Dastardy Duo from the Left Tunnel, the earliest incarnation of the Delightfuls, and the latter, having heard about the Dastardly Duo from Father, are happy to make their acquaintance. The Dastardly Duo ask for the DCFDTL's help in annihilating the Kid Ninjas, with the incentive being that they can destroy both KND's in one fell swoop. The Delightfuls laugh, but the Dastardly Boy shuts them up by saying that noise, obviously, bounces off the rock walls of the Dojo.
Blast from the KND Past
Meanwhile, Numbuhs 2, 3, 4, and 5 have stumbled upon the Kid Ninjas' "Med Lab". They are relieved to find Numbuh 1 alive and well, and even more delighted to see the Kid Ninjas from the Dojo for the first time. Apparently, there are five members in the Kid Ninjas, just as there are in Sector V: Alpha, Beta, Gamma, Delta, and Epsilon (the first three are boys, the latter two, girls). Numbuh Three even discovers Numbuh Epsilon has her own private Rainbow Monkeys collection, of which Epsilon is very protective. The reunion is interrupted, however, by the DCFDTL's entrance. They introduce their "primitive counterparts", the Dastardly Duo, who are in their "Secret Weapon", which resembles a cross between Senior Citizen and the R.R.I.D.M. Both KND attack the Weapon, with the Sector V team wielding their S.P.L.A.N.K.E.R.'s, but the DDFTLT manage to defeat them. As the Secret Weapon steps up to the grounded Kids Next Door and Kid Ninjas, a whirring sound in the wall announces the arrival of the DNK H.O.R.N.E.T.T. (Huge Overland Rover digs Neatly to Explore Tough Terrain), with Eizzil driving. The H.O.R.N.E.T.T. and the Secret Weapon engage in battle, but the H.O.R.N.E.T.T. comes out victorious, sending the Weapon blasting through the roof of the Dojo, and the Delightfuls follow shortly afterward.
Call Us, Beep Us
The Kid Ninjas thank the KND and DNK for their assistance, and they also tell the two teams that, even though the Kid Ninjas will always be allies to the Kids Next Door, they have a lot of work to do in their Dojo before they can join in the major battle against the adults (particularly fixing that hole in the wall). Numbuh 3 asks Negative Numbuh 3 where the M.O.M.S.T.E.R. went, but Negative Numbuh 86 tells her not to worry about it. The KND head back to the S.C.A.M.P.E.R. and the DNK to the H.O.R.N.E.T.T., and as they lift off into the sky, the Kid Ninjas from the Dojo wave good-bye. The Fanfic ends on that happy note.