This article focuses on the relationships between Numbuh 2 and other members of the show.
Numbuh 2 shares a love-hate relationship with his younger brother. He may find Tommy annoying most of the time, but he seems to show concern for him once in a while. In Operation: T.R.I.C.Y.C.L.E., when Tommy confronted his Tommymobile, he realised it went on rampage because he abandoned it before, and showed up before it did Tommy any harm.
Numbuh 2 is still very close to his dad despite his apparent death. He heard him from the skies in Operation: C.A.K.E.D.-F.O.U.R. which motivated him and Betsy. Numbuh 2 was the only one to believe in Betsy, his (and his father's) inner tube, which even saved every other kid when it deflected Father's attack and broke the cake batter.
Not much is shown of his relationship with his mom, but he once gave her a tip before she left home in Operation: S.I.T.T.E.R.. In Operation: M.I.N.I.-G.O.L.F., Numbuh 2 waves to the camera and says "Hi Mom!".
Numbuh 2 has a one-sided relationship with his grandmother. As shown in Operation: T.A.P.I.O.C.A., she is herself a villain and is one of the few characters who is openly intolerant of her grandson's puns. She sometimes whacks his head with her walking stick and mistakes him for his younger brother, Tommy.
Their friendship may be quite close, as Numbuh 1 mentioned him as being his childhood friend in Operation: Z.E.R.O.. Numbuh 2 also took it the hardest (besides Numbuh 4) when Numbuh 1 left for the GKND in Operation: I.N.T.E.R.V.I.E.W.S..
Numbuh 2 seems to have a close friendship with Numbuh 4, as both of them alone appeared in many episodes including Operation: S.A.F.E.T.Y.. In Operation: F.I.S.H.Y., when Numbuh 4 went insane over getting back Numbuh 3's fish, he was moved when Numbuh 2 reminded him of their friendship.
Numbuh 3 and 2 share a mutual concern for Bradley, such as when they first found him in Operation: C.A.M.P.. They also worked on his injuries and rebuilt him together in Operation: H.O.S.P.I.T.A.L., and they had a mission in Operation: S.I.X., involving Bradley.
Numbuh 2 and The Kid are friendly rivals that were first pitted against each other by the crazed Mr. Washer when they kept on leaving chili dog stains on his counter. After learning the truth and teaming up to stop Washer, Numbuh 2 offered him a place in the KND, but The Kid politely declined. Nevertheless, they seemed to become friends.
He first encountered Mr. Fizz during a soda bar raid in Operation: P.O.P., after Mr. Fizz raised the minimum soda consumption age to 13, much to Numbuh 2's anger. He was interrogated for his role in the situation, but his teammates helped him escape. During the battle in the bottling plant, he repeatedly shook the machine's lever, causing Mr. Fizz to feel dizzy and the carbonation to blow his suit to smithereens.
Like all his teammates, Numbuh 2 generally dislikes the Delightful Children From Down the Lane.
Unlike everyone else in the show, Numbuh 2 is the only one who enjoys Grandma Stuffum's cooking, although he himself said her food was 'disgusting', saying cheesy phrases like, "It's snack time, Fraulein!" or, "I'm sending this dish back to the kitchen", much to Numbuh 5's chagrin.
Hoagie bought supplies from Mr. Washer until Mr. Washer got sick of him leaving chilli dog stains on the counter and set him up against The Kid.
Even though this relationship is not strongly implied like Numbuh 4 and Numbuh 3's, the two flirt in their own subtle ways, such as Operation: K.I.S.S., where Numbuh 5 states that she'll keep Cree's CD's and her "boyfriend" (Numbuh 2, who was "Hank") nice and safe. In Operation: D.A.T.E., Numbuh 5 quickly leans on Numbuh 2 when choosing her date. In Operation: C.O.U.C.H., when Numbuh 2 mentions Numbuh 10 is "easy on the eyes", Numbuh 5 quickly elbows him.
Their relationship is usually seen through the many bad puns of Numbuh 2, making their relationship somewhat tsundere; Numbuh 5 usually can't stand his puns such as in Operation: R.A.B.B.I.T. and Operation: Z.E.R.O.. Besides this, they are also seen without Numbuhs 1, 3 and 4 in several episodes, including Operation: P.A.R.T.Y. and Operation: C.L.O.W.N.. In Operation: P.I.R.A.T.E., Numbuh 2 is the one who says she is the best when she brings back the candy, saves her from her fall from walking the plank, and asks if she is okay. Numbuh 2 worried for her when she got anxious over the destroyed Ice-cream Storage Facility in Operation: C.A.K.E.D.-F.I.V.E..
They often make fun of Numbuh 4 for his crush on Numbuh 3, and at Numbuh 1 for his relationship with Lizzie for different reasons. Throughout the series, they are seen to have a close friendship and in Operation: I.N.T.E.R.V.I.E.W.S., it was revealed that they got married.
There have also been many episodes when Sector V has to split up, Numbuhs 2 and 5 usually end up together/alone together.
In Operation: K.I.S.S., Hoagie starts to display a crush on Numbuh 5's older sister, Cree Lincoln. When he transforms himself into a teenager, Cree shows attraction towards him and even kisses him multiple times before he turns back to normal. Cree hates him afterward because he's a KND operative, but Numbuh 2 continues to harbor a crush on her and constantly tries to flirt with her, most notably in Operation: S.I.T.T.E.R.. Despite this he apparently realized this was an infatuation as he eventually married Numbuh 5.
In Operation: C.O.U.C.H. he seems to have a crush on her.