"The King does not pretend!"
-- King Sandy
King Sandy is an enemy that the KND have dealt with a couple of times.
King Sandy has buckteeth, freckles under his eyes, and sandy-blonde hair. He wears a yellow T-shirt, orange swim-shorts, a green cape (possibly a towel), and bare feet. On his head, he wears an orange bucket (meant to be his crown) with shells around its edges, and a bigger shell on its center.
He is young boy who thinks he is a king and had a crush on Kuki, who he considered his "princess", and later, his "queen". He later develops a mutual crush on Mushi instead. He is served by the "Knights of the Round Towel", who are actually his older cousins. Sandy first appeared in Operation: B.E.A.C.H., residing in an over-sized sandcastle.
He meets Kuki when his Knights bring her to his sand castle stating that she was found building a castle of her own on the beach. He is intrigued by her beauty and asks her to be his queen - Kuki, who believes this is all a fun game, says yes, when she doesn't realize he is serious.
Meanwhile, Wallabee is seen telling Hoagie and Abigail about Kuki being kidnapped and suggests that they get her back. Hoagie and Abigail exchange devious glances and ensue chanting "Wally and Kuki sittin' in a tree, K-I-S-S-I-N-G!" In reaction, Wallabee makes an excuse about Kuki owing him a quarter, so they must retrieve her.
Back in the castle, King Sandy watches Kuki as she admires her pretty wedding dress, but soon spies Sector V (minus Nigel) fighting his Knights after infiltrating the castle to rescue Kuki. When Numbuh 3 asks about the commotion, he insists they hurry the marriage along and the run to the tower. As they are running up the sand stairs along the wall of the tower, Kuki spots Wallabee as he fights and calls out to him. When he looks up, she happily exclaims that she's getting married, which shocks him; he steps back too far and falls over the edge of the balcony to the sea and then passes out.
When he finally wakes up, he, Hoagie and Abigail are tied to a sand column in the tower, close enough to witness the "marriage ceremony" being preformed by a surfer-esque lifeguard. Wallabee asks Kuki is she's really getting married, and she assures him that they're only pretending: King sandy overhears her and shouts his catchphrase, "The king does not pretend!" He and Kuki argue about it, her claiming that she's only 10 years old, and he replies that he likes older ladies. Shortly after a pause, she still refuses to marry him for real, so he decides to force her to go through with it. Wallabee then breaks free and after knocking his Knights off the wedding room to the balconies, he begins to fight him - however, the lifeguard asks how long the ceremony will be because he's worried about the tide coming in soon.
Upon learning this information, the kids separate and the sand castle is struck at the base by rough water coming in fast for High Tide. While Hoagie, Kuki, Wallabee, and Abigail escape, the castle collapses and King Sandy falls to his aparent doom along his Knights. At first, King Sandy's fate seems to be unknown like his Knights', but out of the rubble pops up King Sandy and his Knights revealing their survival. He yells after them that he will return, and then his mother is heard off-scene telling him to come back with his cousins. They make their leave with King Sandy still enraged about his failure.
He returned in Operation: K.A.S.T.L.E., his castle this time located "Rainbow Monkey Happy Sugar Land", and tries to force Kuki to marry him, threatening to dump several Rainbow Monkeys into a pot of boiling nacho cheese. Just as they're about to get married, Kuki's little sister Mushi arrives to explain that he can't marry Kuki and explains the pretend story. After the king shouts "THE KING DOES NOT PRETEND!!!!", Mushi explains that her sister is like 10 years old and thus, the king can't really marry her and Kuki jumps in. As Sandy gets on the boat, swearing revenge on Mushi until he sees how she looks, he abandons his pursuit of Kuki and falls in love with Mushi.
At the end of Operation: S.P.A.N.K.E.N.S.T.I.N.E., Sandy is seen helping Mushi escape from her room after being grounded. Sandy and Mushi make their final appearance in Operation: I.N.T.E.R.V.I.E.W.S., stealing Professor Triple Extra Large's perfect snowcone during the scavenger hunt.
- Sandy also appears in the game, Rainbow Monkey Rundown on Cartoon Network's website, based on Operation: K.A.S.T.L.E., where you play as Kuki as she escapes from his castle. Sandy appears as the final boss of the game.
- Sandy is one of many villains in cartoons, live-action TV and movies to use the common trope of choosing female protagonists as (usually unwilling) queens in their world domination schemes, though unlike other examples he actually gets a mutual love interest. He is the first KND villain to use this trope; the second is James Nixon McGarfield.