Sector Z was a Kids Next Door sector who Father turned into The Delightful Children From Down The Lane. Monty Uno recommissions them to help defeat Grandfather. The effect was temporary due to the severe effect on having stay delightfulized.
The only known appearance of Sector Z within the KND series is between Season 5 and Season 6.
In Operation: Z.E.R.O. the identities and the cause of the missing operatives is revealed after Monty Uno uses the recommissioning device created by himself on the DCFDTL.
This then caused The Delightful Children from Down the Lane to revert back to the Kids Next Door operatives of Sector Z. However after recommissioning, the DCFDTL learned that the effects of the recommissioning module on them was temporary, as the Delightfulization process was severe, so Sector Z have to use their limited time to save the world before reverting back to their Delightful forms.
As Sector Z, they wear heavily-clothed samurai fatigues. Unlike their delightful selves' white and blue clothing, Sector Z's has some gray/black and red/green features to show their brave nature.
Individually: David's hair covers his right eye instead of fully as a delightful, Bruce's hair slightly straights out, Constance's hair is messier and a lighter shade of brown, Lenny does not have braces, and Ashley's hair is golden yellow instead of sandy blond as a delightful.
Defeated Sector Z
After structuring a plan to defeat Grandfather, Numbuh 1 and Sector Z depart to KND Moonbase. While Monty Uno and Father distract Grandfather and give the kids time to conduct the plan into effect. As Nigel Uno arrives on the bridge, he is attacked by his former teammates from Sector V; Numbuh 2, Numbuh 3, Numbuh 4 and Numbuh 5 as Senior Citi-Zombies. Nigel Uno between his mixed feelings doesn't fight but help then arrives as Sector Z comes to Nigel's aid.
As Sector Z fight the former members of Sector V, Numbuh 1 sets the plan into action, but another problem arises. Sector Z may have disabled Numbuhs 2, 3, 4, and 5. However, the temporarily effects of recommision wear off and Sector Z reverts back to the Delightful Children From Down the Lane but not without telling him to tell that they'll miss KND.
After this encounter, the members of Sector Z are only seen as the Delightful Children. By the end of the film, Numbuh 1 is the only one who knew of their previous lives, and no attempts are made to revert Sector Z to their original state for reasons unknown.