Numbuh 1 (a.k.a. Nigel Uno) is the main protagonist from Codename: Kids Next Door, and the leader of KND Sector V.
Billy & Mandy Moon the Moon
Numbuh 1, alongside the rest of Sector V makes a cameo appearance in the alternative credits stinger for the episode. After the moon is filled with cheese, it cuts to the team playing video games on the Moonbase. After a while, Nigel asks if anyone else smells cheese, with everybody turning eyes at Numbuh 2, who proceeds to say that he didn't "cut it".
The Grim Adventures of the Kids Next Door
Numbuh 1 appears in Billy's house along with the rest of his team, the Sector V, to try to take Billy's pants from his father, Harold, with the scythe embedded in them. Seeing that did not work, Numbuh 1 proposes to the team lead Billy to KND Deep Sea Lab to try again while he disguised as Billy to impersonate in his absence.
When the plan starts, Mandy and notes appear at first glance that Numbuh 1 is not Billy, and catch him to confess his true identity. Once Numbuh 1 confesses, Mandy pulls off her glasses to impersonate him and get to control all the Command KND. Numbuh 1 manages to break free and run to stop, but is captured by Grim, to tell him where the scythe is because this did think that Numbuh 1 is Billy. Grim tried to torture him using the Bone of Barnacles, but falls to feel that The Delightful Children From Down the Lane have been merged with the scythe. Numbuh 1 fail to escape, but when Grim tells him what has meaning, Numbuh 1 is allied with Grim and catch a ship to go to the KND Moon Base. During the flight, both are arrested by Numbuh 60, who takes prisoners to Mandy. That's when this tells them to Numbuh 1 and Grim their malefic plans, ordering after his incarceration. After being released later by Numbuh 5, use the Bone of Barnicles to merge with Numbuh 1 thus creating a giant warrior controlled by the young.
Upon reaching Endsville, Numbuh 1 prepares to fight Delightful Reaper, but Harold pants protect their attacks. Once Harold removes his pants to Delightful Reaper, Numbuh 1 uses his sword to finally destroy it. After that, return to the KND Moon Base where after witnessing the flight of Mandy, Harold confuses Numbuh 1 is Billy, tugging at the ear and scolding him for what happened while trying clarify Numbuh 1 is not Billy.