This article focuses on the relationships between Numbuh 1 and other members of the show.
Family
Monty Uno (Numbuh 0)
- "Dad...you ARE Numbuh 0... Oh, my gosh! I can't believe it! I can't wait to tell everyone! They'll be like, "You're the coolest, Numbuh 1!", and then I'll be like, "Yeah, I am, aren't I?". And then we'll go on missions together and battle evil adults and AHHH!!! My own dad is really Numbuh 0!" - Numbuh 1 in Operation: Z.E.R.O.
Monty or "Numbuh 0" is Numbuh 1's dad. He's famous for bringing the KND to its seventh age. During Operation: O.O.M.P.P.A.H., Numbuh 1 is embarrassed that he's his dad however towards the end of the episode, he fights for his dad back from Willard (a lonely kid who wants his own dad to pay attention to him). Then, this changes the relationship between Numbuh 1 and Monty as he takes up playing the sousaphone (not tuba).
In Operation: E.N.D., Numbuh 1 takes the opportunity to spend some quality time with him though it changes when Numbuh 86 and her decomissioning squad chases them. Later in that same episode, he mourns about how he wanted to spend quality time with him.
Numbuh 1 and Monty in Operation Z.E.R.O..
Everything starts to change during Operation: Z.E.R.O. when Numbuh 1 first yells at him to shut up because Monty only babbles on about spending quality time as he's oblivious to what's happening around them (even when they're being chased by Citi-zombie Hamsters). Once Numbuh 1 uses the recomissioning device on his dad, he instantly becomes Numbuh 0 once again, leading to Numbuh 1 spazzing as he can't believe that his own dad is Numbuh 0.
The two go out of their way to defeat Grandfather and save the entire world. At the end of the movie, Numbuh 0 gets decomissioned along with Grandfather. Numbuh 1 tries to figure out what's wrong with the recomissioning device though he gets a message that he shouldn't recomission Numbuh 0 because his greatest mission is "Being a good father to my son Numbuh 1.". This makes him cry and Monty coming up from behind and asking what's wrong. Numbuh 1 hugs him and tells him it was just an old friend.
In Operation: I.N.T.E.R.V.I.E.W.S., Monty becomes Numbuh 0 one more time along with his wife, Numbuh 999, to wish him off and tell him that he's proud of him to become the first Earth representative operative of the Galactic Kids Next Door.
Numbuh 999
- "You were in the Kids Next Door, too?!" - Numbuh 1 in Operation: I.N.T.E.R.V.I.E.W.S..
Numbuh 999 is the wife of Monty Uno and mother of Numbuh 1. Not much is known about their relationship to each other, but she seems to be a jolly English woman who does everything a mother should do for their son. In Operation: I.N.T.E.R.V.I.E.W.S., she reveals that she is proud of her son as well.
Numbuh 10
"And I think this is the first time I'm actually relaxing a bit instead of constantly thinking about missions and stuff." -Numbuh 1 in Operation: H.O.L.I.D.A.Y. In Operation: H.O.L.I.D.A.Y., Lizzie suspects that Numbuh 1 is cheating on her with Numbuh 10 and arrives at Sector J with Numbuh 2 and Numbuh 3 in tow. Numbuh 1 and Numbuh 10 tell her that they aren't dating, but that Numbuh 10's father is his mother's long-lost brother, making them cousins.
Love Interests
Lizzie breaks up with Numbuh 1 in Operation: G.I.R.L.F.R.I.E.N.D.
Lizzie Devine
Lizzie was Nigel's girlfriend for almost the entire series until Operation: G.I.R.L.F.R.I.E.N.D. where they split up. In episodes with her, he's always looking out for her even when she's driven him to the point of madness such as Operation: L.I.Z.Z.I.E. where she puts a boyfriend helmet so that he would pay more attention to her.
In Operation: D.A.T.E., it can be inferred that when he was still together with her, and must have spent quality time with her due to all of the myriads of pictures she had of him or where they were together. However he is usually too busy with the KND to go on a date, which is frusturates Lizzie. Though, in Operation: S.N.O.W.I.N.G., he had to save her from being the President's girlfriend. The two are also shown to be very close in Operation: P.O.O.L..
However, in Operation: G.I.R.L.F.R.I.E.N.D., the relationship is hinted throughout the episode to the end that it will end. Lizzie realizes that, after Nigel saves her from the Treehouse, she can't compete with the Kids Next Door anymore and she wants a boyfriend who is willing to pay more attention and love towards her. Numbuh 1 tells her not to go away though she goes away leaving him to shed a tear at the end of the episode.
It seemed that even though they were together at a long time, their relationship cannot work out since she wanted Numbuh 1 to turn his back on missions for a date. Even though Numbuh 1's purpose was for the KND. He could only be with someone who understands his passion.
Friends
Numbuh 362
Numbuh 1 and Numbuh 362 after the events of Operation: G.I.R.L.F.R.I.E.N.D.
Numbuhs 1 and 362 are seen to be very close throughout the series, as they call themselves by their first names. In Operation: I.T., they are shown working together to reclaim the KND from Father. At the end of Operation: Z.E.R.O., they are seen casually talking with one another. The two are seen having lunch together in Operation: G.I.R.L.F.R.I.E.N.D.. When Lizzie breaks up with him, Rachel tries to cheer up Numbuh 1. Numbuh 362 has a high opinion of Numbuh 1's sector.
Numbuh 5
Numbuhs 1 and 5 are close friends. In Operation: U.T.O.P.I.A., she is concerned with his safety after contact was lost with him. They, in Operation: L.I.C.E., are the last remaining two in the Cheese Room. In Operation: I.N.T.E.R.V.I.E.W.S., Numbuh 1 compliments Numbuh 5, saying she's the only one in the sector with any real common sense.
Numbuh 4
Numbuh 1 is one of Numbuh 4's best friends, as stated in Operation: B.R.I.E.F.. When Numbuh 1 is leaving for the Galactic Kids Next Door in Operation: I.N.T.E.R.V.I.E.W.S., Numbuh 4 seems really angry, most likely because he will miss him. When Sector V came to say good bye, Numbuh 4 was crying and told Numbuh 1 he and all of Sector V would come running to help him if ever needed it, showing just how much he cares about Numbuh 1. Later in the episode, a now adult Numbuh 3 states that 4 took it the hardest.
Numbuh 3
Numbuhs 1 and 3 are good friends throughout Codename: Kids Next Door. Despite the two being friends, Numbuh 1 is sometimes annoyed with Numbuh 3's antics and dizzyheadness as seen in Operation: K.A.S.T.L.E. and Operation I.-S.C.R.E.A.M., being opposites. However, Numbuh 1 cares for Numbuh 3 as seen in Operation: H.O.M.E. when he tried to cheer her up after her My First Rainbow Monkey was broken.
They have a brother-sister relationship as seen in episodes like Operation: F.A.S.T.-F.O.O.D., when Numbuh 1 let Numbuh 3 lead a mission for a day, though it was only to pick up burgers, knowing Numbuh 3 doesn't have what it takes to lead a real mission. However, he stated that Numbuh 3 was still part of the team and did not want to hurt her feelings.
It is hinted in Operation: W.H.I.T.E.H.O.U.S.E. that at one point he may have had a crush on her. Adult Numbuh 5 asks him "Who had a crush on Numbuh 3? And don't say Numbuh 4." to which he just gives her a knowing smile. This, however, was most likely a one-sided crush.
In Operation: I.N.T.E.R.V.I.E.W.S., as they say their goodbyes, Kuki gives him a kiss on his head and rubs it while Numbuh 1 looks at her with a smile.
Numbuh 2
Numbuh 2 is another one of Numbuh 1's best friends, as said in Operation: Z.E.R.O.. The two are shown two be very close throughout the series. In Operation: I.N.T.E.R.V.I.E.W.S., Numbuh 2 appears to be very sad when Numbuh 1 leaves for the Galactic KND, packing him "the essentials." Numbuh 2 is really impressed by Numbuh 1's report in Operation: A.R.C.H.I.V.E..
Numbuh 86
Numbuh 1's relationship isn't always so friendly. Usually, 86 is seen yelling at Numbuh 1, as he is a boy, along with Numbuhs 2 and 4. In Operation: C.A.N.Y.O.N., she is impressed with Numbuh 1's idea to fill the Grand Canyon with Rainbow Munchies, until the Toiletnator flushed it all down. Still, in Operation: E.N.D it was revealed that Numbuh 1 and Numbuh 86 went to kindergarten together.
Numbuh 6
Numbuhs 2 and 3 first adopted Numbuh 6, who at the time was simply known as Bradley, in Operation: C.A.M.P.. Numbuh 1 was the only member of Sector V who didn't like him, as he was distracting everyone from the mission. Later in the episode when Bradley's stench helped unhypnotize the campers, Numbuh 1 apologized to him and granted him the title of Numbuh 6. Numbuh 1 likes him through the rest of the series.
Vin Moosk
At first Numbuh 1 doesn't trust Vin Moosk, as he is an adult. Vin Moosk does, however, convinces Numbuh 1 to help him get rid of the ties after explaining he realized ties made him work a boring job. Numbuh 1 tried to help Moosk escape the queen tie when Windsor turned on them, and Moosk sacrifices not having to wear ties so Numbuh 1 didn't have to. Numbuh 1 is saddened by this, saying Moosk was their first cool adult he'd ever met. When Moosk is back at his boring accountant job, Numbuh 1 sends him some spray starch to get rid of the ties.
Enemies
Grandfather
Grandfather is one of Numbuh 1's most hated enemies, even though he is his real grandfather. When Grandfather has Senior Citi-zombified most people on the planet, Numbuh 1 teams up with his dad in order to restore the world, and succeeds in doing so. Something that really adds to the disliking factor is that Grandfather Senior Citi-zombified all of his friends.
Father
In Operation: G.R.O.W.-U.P., Father sent the DCFDTL to destroy the KND, they turn Numbuh 1 into an adult. Numbuh 1 battles Father on many occasions, such as in Operations G.R.O.W.-U.P. and C.A.K.E.D.-F.I.V.E.. They had a short truce Operation: M.U.N.C.H.I.E.S because Knightbrace was going to destroy the last box of Rainbow Munchies, and "Desperate times call for desperate measures." In Operation: Z.E.R.O, Numbah 1, his father and Father (who is revealed to be his uncle), band together once more to stop Grandfather.
Delightful Children From Down The Lane
The Delightful Children From Down The Lane are perhaps Numbuh 1's greatest enemies, despite being his cousins. For starters, they made him lose his hair, which he thought was really cool. Secondly, five times a year they have their birthday cake and try to keep it all to themselves. Thirdly, they are always trying to destroy the KND.
On only four occasions do Numbuh 1 and the Delightful Children get along.First was in Operation: Z.O.O. when they work together with his Zector to breakout of their cages in a Zoo, Second is Operation: I.T., when they gave him and Numbuh 362 the C.O.D.E.M.O.D.U.L.E..to track down Father to stop him The third was is in Operation: Z.E.R.O., where the DCFDTL are out of their delightful state to help Numbuh 1 defeat Grandfather. The last is in Operation: P.A.R.T.Y..
Chester
Chester imprisoned Numbuh 1 in a fantasy world in order to make money in Operation: U.T.O.P.I.A..
Willard
Willard is perhaps one of Numbuh 1's greatest enemies, since Willard stole is father from him. Numbuh 1 is willing to fight Willard by any means necessary to get his dad back, even play a sousaphone. Numbuh 1 plays the instrument for as long as he can.
Mr. Boss
Numbuh 1's greatest hatred for Mr. Boss was shown in Operation: D.A.D.D.Y.. When Mr. Boss cut Numbuh 85's hair to an indescribable disaster and was going to do the same to Shaunie, Numbuh 1 was very angered, most likely because he'd lost his own hair already. Numbuh 1 also declared Mr. Boss his sector's archenemy. Like most villians, Numbuh 1 has a general dislike for him.
Rivals
Chad (Numbuh 274)
Numbuh 1 was close with Chad when he was a cadet, choosing Chad to be his mentor. Numbuh 1 admired Chad until Chad betrayed the KND. At the end of Operation: T.R.E.A.T.Y. when they were dueling, Numbuh 1 kept scolding Chad. When Chad was revealed to be a TND agent, Numbuh 1 stood down. After Numbuh Infinity's and Chad's departure, Numbuh 1 was pretty sad. Both of them are two of the greatest KND operatives ever.
James Nixon McGarfield
Numbuh 1 and Jimmy are shown to be on good terms in Operation: P.R.E.S.I.D.E.N.T., with Numbuh 1 being encouraging and supportive of the then-4th Grade President. But by Operation: S.N.O.W.I.N.G. they have become enemies, especially since Jimmy kidnapped Numbuh 1's girlfriend Lizzie and tried using a modified boyfriend helmet to make her his girlfriend against her will.