History TearJerker / CodenameKidsNextDoor

* Meta Example: This was the very last of the famous Cartoon Cartoons....ever (not counting ''GrimAndEvil'' getting split into [[WesternAnimation/TheGrimAdventuresOfBillyAndMandy two separate]] [[WesternAnimation/EvilConCarne cartoon shows]]); think about that for a bit....yeah, hurts, doesn't it?

* Meta Example: This was the very last of the famous Cartoon Cartoons....ever (not counting ''WesternAnimation/GrimAndEvil'' getting split into [[WesternAnimation/TheGrimAdventuresOfBillyAndMandy two separate]] [[WesternAnimation/EvilConCarne cartoon shows]]); think about that for a bit....yeah, hurts, doesn't it?

* Meta Example: This was the very last of the famous Cartoon Cartoons....ever (not counting ''WesternAnimation/GrimAndEvil'' getting split into [[WesternAnimation/TheGrimAdventuresOfBillyAndMandy two sepa]] [[WesternAnimation/EvilConCarne rate shows]]); think about that for a bit....yeah, hurts, doesn't it?

[[caption-width-right:350:''Stay young...'']]

* Numbuh One being forced to fight his former teammates. Fortunately, Numbuh Two's birthday suits help turn them back to normal.
* Numbuh Five's heroic sacrifice.

* Operation K.A.S.T.L.E.: King Sandy torturing Rainbow Monkeys...and giving a Scarpia Ultimatum where he'll dip Rainbow Monkeys in nacho sauce if she doesn't agree to marry him.

** Or later on, [[spoiler:when we see Numbuh Zero once again as Numbuh One's bumbling dad, with no memories of being a KND operative. "Just playing with an old friend, Dad."]]

** [[spoiler: After the arguments between the various aliens is silenced by whomever is in charge, they say its his choice to make. After a moment of hesitation, he makes a saulte while stoically shedding a single tear and proceeding to activate the device.]]

** Zero does get recommissioned one last time, in the series finale... [[spoiler: to say goodbye to his son forever, as Numbuh One leaves for the Galactic Kids Next Door.]]

** Numbuh Zero's final message to Numbuh One via the broken recommissioning module at the end of ''Operation Z.E.R.O.'' is both heartfelt and heartbreaking, saying that while he might not remember what he did, he wants to go on his greatest mission: [[spoiler:being a father to his son.]]

--> '''Numbuh Zero''': "I'd love to stay and have lots more adventures with the super cool Numbuh One, but... Im not a kid anymore."
** Zero does get recommissioned one last time, in the series finale... to say goodbye to his son forever, as Numbuh One leaves for the Galactic Kids Next Door.

-->'''Numbuh Five:''' My sister's a teen! The greatest operative I ever knew is a teen! Look at me. I'm practically a teen now!

* "Operation: O.O.M.P.P.A.H" Numbuh 1's father takes him on a fishing trip to bond. After a day of boredom and annoyance, Numbuh 1 snaps at his father and the camera pans up show his face and he just looks heartbroken.
-->'''Monty Uno:''' I'm sorry, Nigel. I just wanted to be your friend.\\
** Showing his face, notably, as prior to this, it had been [[TheFaceless obscured]], showing it swiftly shifts the mood.

-->'''Numbuh One:''' Just promise me one thing, that you'll never grow up, not even if you live to be a hundred and don't have any memories of our adventures together, you'll still be a kid at heart.

KidsNextDoor may be a kids show, but it can still be sad!

* "Operation: O.O.M.P.P.A.H" Numbuh 1's father takes him on a fishing trip to bond. After a day of boredom and annoyance Numbuh 1 snaps at his father and the camera pans up show his face and he just looks heartbroken.
-->'''Monty Uno:''' I'm sorry Nigel, I just wanted to be your friend.\\

* The ending of "Operation: I.N.T.E.R.V.I.E.W.S. Adding extra weight to it? It's the audience's goodbye as well. It's been a great six season run, and seeing it come to an end is just heartbreaking.

** Decommisioning itself is a gloomy process. Imagine losing most of your memories from your childhood. Imagine forgetting your crushes and your best friends, and acting like they never existed.

* The ending of "Operation: I.N.T.E.R.V.I.E.W.S.? Adding extra weight to it? It's the audience's goodbye as well. It's been a great six season run, and seeing it come to an end is just heartbreaking.
-->'''Numbuh One:''' Just promise me one thing, that you'll never grow up, not even if you live to be a hundred and don't have any memories of our adventures together, you'll still be a kid at heart.

* "Operation: M.A.T.A.D.O.R."
** Numbuh Four is having fun in his time as a "bully fighter", playing matador to caffeinated adults who act like bulls. The heavy stuff comes when at the championship, his next adult to fight is [[spoiler:his father (whose face is shown for the first time)]].
** Also when he learns the dark side to the fights: [[spoiler: adults are lured, captured and thrown into pens and force-fed enough caffeine to make them charge at anything, even their own kids. Numbuh Four's Dad got roped into the whole mess because he believed he was going to a seminar... on ''being a better dad''. OUCH.]]
* The [[http://images4.fanpop.com/image/photos/18100000/Stay-Young-codename-kids-next-door-18179248-2334-1594.jpg last image]] from the series is enough to make anyone bawl.
* In Operation C.A.R.A.M.E.L we learn why Heinrich holds ill will towards Numbuh 5. 5 years, 5 months, and 5 days earlier an incident happened that gave Heinrich delicious caramel unknowingly at the cost of what he valued most. Turns out he used to be a female and she had lost what she had valued most, her beauty. Assuming Heinrich is 10 like Numbuh 5, this means Heinrich lost what he had valued most when he was only 5. At such a young age losing something that important to you would do severe psychological damage.

** Showing his face notably as prior to this it had been [[TheFaceless obscured]], showing it swiftly shifts the mood.

** Showing his face notably as prior to this it had been [[TheFaceless obscured]], showing it swiftly shifts the mode.

* "Operation: O.O.M.P.P.A.H" Numbuh 1's father takes him on to bond. After a day of boredom and annoyance Numbuh 1 snaps at his father and the camera pans up show his face and he just looks heartbroken.