Numbuh 2K.O is mostly an unknown operative and is the mechanical one, which is why he is makes inventions for Sector UNK. The location of the Treehouse is a top secret thing to know, of course, not to the rest of the KND organization. He is good friends with Numbuh G, who was Numbuh GGG in her days in Sector UNK, but disappeared from it and the KND for a whole year and came back only to join Sector QU.