"Aww, geez! It's the Toiletnator!"
Mr. Boss is a corrupt, child-hating, corporate executive who acts as the de-facto leader of the KND's standard rogue's gallery.
He is very physically large, has a bald head, a mustache, an over sized cigar in his mouth, and a hunched back.
In Operation: D.A.D.D.Y., Numbuh 1 describes Mr. Boss as his sector's arch-enemy (probably because Grandfather, Father and the Delightful Children From Down The Lane would all be considered enemies of the entire organization, rather than just Sector V). He is the second in Command of the villians after Father.
Mr. Boss first appeared in Operation: O.F.F.I.C.E., in which he attempts to send all his employee's daughters, including Numbuh 3, to Pluto so that his workers wouldn't have any children to go home to and could spend more time serving him. His plans are foiled by Numbuh 3 and Numbuh 4, who fortunately had been brought to work by his father despite it being "Bring your daughter to work day".
Mr. Boss is often the holder for mass gatherings of villains, such as those in Operation: M.O.V.I.E. and Operation: F.L.U.S.H., where he and his guests attempt to formulate plans to destroy the Kids Next Door.
Another major plan of his was stealing the Rainbow Monkey Lisa, and attempting to eat it in Operation: M.A.C.A.R.R.O.N.I. His plan was stopped by Numbuh 13, who did so by destroying the macaroni painting, creating the same end result of the painting's loss.
In Operation: D.A.D.D.Y., it is revealed that Mr. Boss is the father of Numbuh 86, as well as her two brothers Patrick and Shaunie Fulbright. He insists on giving his kids haircuts himself rather than paying to get their hair cut by a professional (with disastrous results). He and his daughter apparently did not know of each others agenda's at all prior to this incident. Mr. Boss at first tried to deny his villainous nature to his daughter until Numbuh 1 reminded him of his plan to send his employees' daughters to Pluto. His response was, "Not my daughter, I love my kids! It's everyone else's I hate." However Boss allowed his kids to remain KND agents rather than see them cry, as long as he could continue fighting them with his friends. He was at the Convention Center in Operation: Z.E.R.O. and a participant in the scavenger hunt in Operation: I.N.T.E.R.V.I.E.W.S..