The Annoyingly Cute Triplets Who Lived Upon the Hill (ACTWLUH) are little girls who were once enemies of the Kids Next Door. They were rich and during the 19th century they stole the cake and refused to share it. Their descendants include Delightful Children From Down the Lane and Numbuh 1. One of the triplets may have been Grandfather's mother. They probably act separately. When the KND attacked the Alamode to get the recipe, however, Numbuh 19th Century accidentally set off a bomb in which five thousand operatives were frozen and decommissioned.
- The Annoying Cute Triplets Who Lived Upon The Hill appears to be a parody of possibly Red Skull or H.Y.D.R.A. since their archenemy Numbuh 19th Century is a parody of Captain America.
Recurring Villains: Toiletnator | Mr. Wink & Mr. Fibb | Count Spankulot | Gramma Stuffum | Stickybeard | Knightbrace | Common Cold | Mr. Fizz | Crazy Old Cat Lady | Professor XXXL | Chester | Henrietta Von Marzipan | Mega Mom & Destructo Dad
Adult Villains: The Proper Patrol | Mrs. Goodwall | Mr. Mogul | The Great Puttinski | Nurse Claiborne | Cheese Shogun Roquefort | Coach Wetterhahn | Mrs. Dirt | Robin Food | Dodgeball Wizard | Black John Licorice | Principal Sauerbraten | Principal Smelling
Child Villains: Madame Margaret | King Sandy | Six-Gum Gang | Interesting Twins From Beneath the Mountain | James Nixon McGarfield | Anna Worthington | Valerie | Annoyingly Cute Triplets Who Lived Upon the Hill | Numbuh 30c | Munshi Saban | Windsor | Girl Squad | Crayon Boy