What if some of the adults still remembered being part of the K.N.D., this is their story and you'll be quite surprised which adults remember.
Numbuh 0.1: Mr. Boss, real name: Edgar Fulbright, weapon of choice: High-tech Ultimate Mustard Pelter, Second in command
Numbuh 0.2: Count Spankula, real name: Vladimir Alucard, weapon of choice: Super Powerful Anti Nemisis Cape, Strategist
Numbuh 0.3: John Wink, weapon of choice: Any 2x4 technology, Weapon specialist
Numbuh 0.4: Timothy Fibb, weapon of choice: Any 2x4 technology, tech specialist
Numbuh 999: Mrs. Uno, full name: Mary Uno, weapon of choice: Specialized Mechanical Adversary Smarting Hands, Hand-to-hand specialist, group trainer.
Numbuh 0: Monty Uno, weapon of choice: Any 2x4 technology, Founder and leader of the Adults Next Door.
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Begin Transmission
A figure is seen walking down the street, the figure appears to be heading towards an abandoned building. The figure goes around to the back of the building, he approached the wall where a DNA scanner and a microphone popped out.
"Kids Next Door Rules." the figure said into the microphone after picking his nose and inserting the booger on his finger into the DNA scanner, a secret door slides open after the DNA scanner goes back into the wall. The figure walks into the room and the door closes, lights shine down on a table in the middle of the room.
"You're late Numbuh 0.1." said one of the people at the table, "I thought you would be here sooner 'Mr. Boss'." said another. "Please don't call me that Numbuh 0, you know how much I don't like being called that." said Numbuh 0.1, aka Edgar Fulbright, as he sat down at the table, "Besides you don't know what it's like keeping this a secret from your kid and wife Numbuh 0, after all your wife is sitting right next to you, Mr. and Mrs. Uno."
"I know it's tough on you but we must keep up our acts until we can reveal ourselves to the Kids Next Door" said Numbuh 0.2, aka Vladimir Alucard, "and we can only hope that the children in the Kids Next Door will accept the fact that there are adult operatives."
"If there's one thing I know about the Kids Next Door it's that they will be shocked, amazed, and possibly outraged at the fact that there are adult operatives", said Numbuh 999, aka Mary Uno, "at least I know my son will. And speaking of the Kids Next Door how's the new 2x4 technology coming along Numbuh 0.3 and Numbuh 0.4?"
"Things are going better than expected, right Numbuh 0.4?" said Numbuh 0.3 aka John Wink.
"Indeed Numbuh 0.3. The new technology and upgrades are going swimmingly." said Numbuh 0.4 aka Timothy Fibb. "Including our hologram projectors. Nobody has noticed that the John Wink and Timothy Fibb they see are in fact just solid holograms projected over our bodies."
"Now then I know this meeting is one of our shorter ones but it's getting late and I believe it's time we went back to our homes and families. Before I adjourn this meeting of the Adults Next Door I would like to thank you all for your performances so far you've done your jobs as undercover operatives well, and I ask if there is any thing left to say." said Numbuh 0, aka Monty Uno. The others shook their heads no. "Then meeting adjourned. Farewell."
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End Transmission
Now this is all AU, but come on, I can't be the only one who thinks that there are adults that still are K.N.D. operatives, after all Numbuhs 2, 3, 4, 5 are shown as adults and it shows them with their memories intact, I'm saying that because they didn't need to be recommissioned for the final episode because they knew that Father would want to get to Numbuh 1 so they faked their decommissioning and led him down the wrong trail. And yes this will become a story.