Numbuh 1 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.
Numbuh 1 is described as the stern, "workaholic leader of Sector V," as he would rather go on missions than spend his day-off at the beach as seen in Operation: B.E.A.C.H. and Operation: B.U.T.T
Numbuh 1 is one of the few operatives in the Kids Next Door that takes his missions seriously as seen in Operation: F.E.R.A.L. where he yelled at Numbuh 86 ("... risking my life, endangered my team and spent valuable KND resources, just to get a stupid key chain?!") when he was sent to Rainbow Monkey Island to retrieve a stone tablet with a secret code on it.
Alongside Numbuh 5, Numbuh 1 is considered the only one with common sense on his team. As the leader, he is quick to jump into action and he is 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 by Numbuh 362 (who notes that he puts his team before himself) that Numbuh 1 is reckless, hot-tempered, stubborn, and acts alone. Nevertheless, he's caring and protective towards his friends, putting his full trust into them.
Numbuh 1 is also a huge believer, as he is one of the few KND operatives who believes in Numbuh 0, who turned out to be his own father.