Throughout the show, he speaks with a noted English accent, because his parents come from England and he was born there, but moved to the United States when he was 3 years old. According to Numbuh 1, he and Numbuh 2 have been best friends since Kindergarten. Nigel had a relationship with Lizzie Devine, who he considered bossy, but deeply cared for until Operation: G.I.R.L.F.R.I.E.N.D. when they broke up.
Nigel usually wears a red turtle-neck sweater, grey shorts, white socks, and brown shoes, which acts as rocket shoes from him when he clicks his heels together. He is seldom seen without his sunglasses and most noticeably of all, he is bald. It’s implied in Operation: F.O.U.N.T.A.I.N. that his baldness was caused by the Delightful Children From Down The Lane and something to do with Numbuh 5 before she recruited him. In Operation: D.A.D.D.Y., he said that he had really cool hair, but it will never grow back again. In Operation: B.U.T.T., it was revealed that Numbuh 1 had a big butt, which is considered funny to the rest of his team.
Numbuh 1 in Operation: I.T.. Added by NinjaSheikNumbuh 1 is described as the sternest, workaholic member in Sector V, as he would rather go on mission than spend his day-off at the beach as seen in Operation: B.E.A.C.H. and Operation: B.U.T.T.. He is one of the few operatives in the Kids Next Door that takes missions seriously as seen in Operation: F.E.R.A.L. where he yelled at Numbuh 86 for, "risking my life, endangered my team and spent valuable KND resources, just to get a stupid key chain?!", when he was sent Rainbow Monkey Island to retrieve a stone tablet with a secret code on it. Alongside Numbuh 5, he is considered the only one with common sense on his team. As the leader, he is quick to action and quite resourceful, but tends to be paranoid to the point of stretching the truth and using his imagination when analyzing a potential adult threat.
In Operation: Z.E.R.O., it was stated many times that Numbuh 1 is reckless, hot-tempered, stubborn, and acts alone by Numbuh 362, who thinks he usually put himself before his team. Nevertheless, he's caring and protective towards his friends, putting his full trust into them. He is also a big believer, as he is one of the few KND operatives who believes in the legendary Numbuh 0, who turned out to be his own father. Although Numbuh 1 is clever, he is also shown to be rather naive in Operation: D.I.A.P.E.R., as he believes that babies were kidnapped and brought to the hospital to be aged into adults and that babies come from "baby eggs".
- Father: Monty Uno (KND former member, Numbuh 0)
- Mother: Mrs. Uno (KND former member, Numbuh 999)
- Grandfather: Grandfather
- Uncle: Benedict Uno/Father
- Cousins: Numbuh 10 & Delightful Children From Down The Lane/Sector Z (Adoptive)
Role in the series
Numbah 1 first met the Shell Louge Squad when they battled against the Delightful Reaper heartless and the Villain League in The Grim Adventures of the KND.