- “Are we men? Or are we KIDS?”
- ―Numbuh 4
Wallabee "Wally" Beatles a.k.a. Numbuh 4 is the brash and impulsive hand-to-hand combatant Australian boy of Kids Next Door Sector V. He is close friends with Hoagie and has a crush on his teammate, Kuki, who is his close friend and team mate and who returns his feelings. He ends up marrying Kuki in the future.
Wallabee is easily recognizable by his blond hair in a bowl cut. He wears an orange hooded sweater, blue jeans and white sneakers. His eyes, like almost the entire Sector V, are not always visible, although it is later revealed that his eye color is green. He is also the shortest Sector V member, for which he is picked on a lot (for example, Abigail called him "sport" in Operation: M.A.T.A.D.O.R.). Another identifiable trait is his Broad Australian accent.
Numbuh 4 is the team's muscle, and the bravest, toughest, strongest, fiercest, wildest, most adventurous, dangerous, courageous, and possibly best fighter in Sector V. These traits are largely due to the fact he is also impulsive, brash, hot-headed, arrogant, ignorant, and the outright harshest of the team. As a result, it is stated in Operation: F.U.T.U.R.E. that his parents would repeatedly send him to boarding schools, but he would always bust out of them.
As seen in Operation: C.A.N.N.O.N. and Operation: F.E.R.A.L., Numbuh 4 has the desire to become leader of Sector V, but fails due to his bossy attitude and lack of intellect. Nevertheless, Numbuh 4 values his friendship with his teammates and cares deeply for them as seen in Operation: P.O.O.L. and even shed tears in Operation: M.A.U.R.I.C.E. when Numbuh 9 was being decommissioned.
One of Numbuh 4's most obvious traits is him exhibiting low intelligence. His sense of history is a garbled mix of irrelevant inaccuracies, as well as the fact he is unable to even spell his own number. Despite not being the most book smart, he is indeed the operative with the most street smarts, along with Numbuh 5, as shown in Operation: M.A.U.R.I.C.E.. Though Numbuh 4's strategies have a history of success, they often end with either high casualties or destruction of the asset he was assigned to protect. Numbuh 4's passion is sports, as shown in Operation: F.O.U.N.T.A.I.N., Operation: M.A.T.A.D.O.R., Operation: D.O.D.G.E.B.A.L.L., and in Operation: B.R.E.A.K.U.P., which is basically the only thing he is good at besides fighting. As it is mentioned throughout the series, Numbuh 4 has a terrible fear of swimming, but was barely able to learn in Operation: P.O.O.L.. As shown in Operation: S.A.F.E.T.Y., Numbuh 4 is possibly hemophobic, as he faints at the sight of his own blood.
As the team's hand-to-hand combat specialist, he the most capable when it comes to physical fighting, but is the least intelligent KND operative as shown in several episodes, including Operation: E.N.D., Operation: D.O.G.H.O.U.S.E., Operation: S.P.R.O.U.T., and Operation: Z.E.R.O., which leads to him being easily fooled, and usually selected for dangerous parts in missions. In Operation: S.P.R.O.U.T., when Numbuh 1, Numbuh 2, and Numbuh 5 were inside of him, it was shown that he had a very small brain. Despite this, Numbuh 4 has a strong sense of determination and never gives up in a fight.
Numbuh 4 can sometimes think that some things that are evil or somebody in trouble aren't a big deal. This doesn't make him beyond reasoning, however. In Operation: M.A.T.A.D.O.R., he didn't think the sport was a big deal because of how the Kids Next Door always fight adults. His teammates, in contrast, say how they fight evil adults while the bullies capture normal/neutral adults and drug them with coffee. Numbuh 4 ignored these claims until he realized they had done the same thing to his father. In Operation: F.O.U.N.T.A.I.N., he at first expressed little concern for Leaky Leona because they barely knew her, but after learning the Delightful Children from Down the Lane were responsible for Numbuh 1's baldness, he changed his mind and helped save her. In Operation: A.M.I.S.H., he assumed the Splinter Cell's goal of getting rid of all adults was cool until Numbuh 5 said the Kids Next Door only fight evil adults, not adults in general.
However, there are some moments where he shows some intelligence. In Operation: P.O.O.L. when the evil versions of the KND (known as the DNK, Destructively Nefarious Kids) posed as his friends, he was able to tell that they were impostors when he looked into Negative Numbuh 3's eyes. He was also able to realize the evil version of him, Negative Numbuh 4, was a coward after discovering that the evil versions of the KND were the opposites of the normal ones. He was even smart enough to attend Harvard as shown in Operation: I.N.T.E.R.V.I.E.W.S.
Numbuh 4 has a strong dislike for everything girly, particularly Rainbow Monkeys, since they make Numbuh 3 giddy. However, Wally begrudgingly tolerates her obsession to stay on her good side, due to his huge crush on her.
He also is shown to be very jealous when someone tries to flirt with Numbuh 3, as seen in Operation: L.O.V.E. and Operation: C.A.K.E.D.-F.O.U.R.. There were many times in the show when Numbuh 4 came close to confessing his love to Numbuh 3, such as in Operation: L.O.V.E., Operation: H.O.S.P.I.T.A.L., and Operation: B.E.A.C.H. , but is never able to finish due to interruptions or an unwillingness to go on.
- Numbuh 1 Disguise (Operation: C.A.N.N.O.N., Operation: Q.U.I.E.T. )
- Sheriff Gear (Operation: N.U.G.G.E.T.)
- Spank Happy Vampire (Operation: L.O.C.K.D.O.W.N., Operation: V.I.D.E.O.G.A.M.E. )
- Numbuh Four Thirtyteen Seven (Operation: S.L.U.M.B.E.R.)
- Matador Costume (Operation: M.A.T.A.D.O.R.)
- Mr. Huggikins (Operation: C.A.T.S.)
- Adult Disguise (Operation: M.O.V.I.E., Operation: C.A.N.Y.O.N.)
- Numbuh 4's last name, Beatles, is a reference to his codename, as the band The Beatles had four members (even though The Beatles originated from the UK, and Wallabee is Australian).
- However it should be noted that Australia was originally a penal colony to the former British Empire in the real world.
- Wallabee's hairstyle is also very similar to the styles of the Beatles in their early years.
- His first name references that he is Australian, as wallabies are native to Australia. Likewise, his brother's name references the kangaroo, specifically a young kangaroo.
- Wallabee is allergic to coconuts, as seen in Operation: O.U.T.B.R.E.A.K., causing him to react with swollen lips.
- He was seen old with grey hair in Operation: F.U.T.U.R.E., Operation: W.H.I.T.E.H.O.U.S.E. and Operation: Z.E.R.O. as a Senior Citizombie. So far, Numbuh 4 has the most future selves seen in the series and movie specials, with a total of six.
- His most prized characteristic, according to Operation: C.A.R.A.M.E.L., is his ferocity, which is a bit simplistic, but very strong.
- A drawing of Kuki is seen in his room near his window in Operation: M.O.O.N., then a picture of a green number 3 with hearts can be seen in the background of his room near a hockey stick, most likely referencing his crush on Kuki Sanban.
- He has a baby grand piano that his mother gave him (Operation: P.I.A.N.O.)
- In the series premiere, The Delightfuls called him "Wallace". It's assumed that was his first name before production.
- He doesn't have a bed in his room in the treehouse, he just sleeps on the floor.
- He appears to be good at impressions, as shown in Operation: Q.U.I.E.T. with Numbuh 1 and in Operation: A.W.A.R.D.S. with Knightbrace.
- He was born in Australia and moved to the U.S. when he was little.
- He is 3 feet and 5 inches, or 104 centimeters in height.
- When asked about how he came about the names for Sector V, Mr W stated that "Wallabee" is about as Australian as you could get.