Lock, Shock, and Barrel are Oogie Boogie's costumed henchmen. They are a trio of children in Halloween garbs of a devil, witch, and skeleton, respectively.
All three of the kids are mischievous, rude and rascally children with no respect for their superiors, taking pride by wreaking havoc and chaos whenever they can. Unlike most henchmen, they are not as evil as their master. They are not loyal to Oogie Boogie.
They are not evil, just mischievous imps, so they are more neutral characters than actual villains, doing horrible things just for entertainment and laughs. It is also implied, however, that they follow Oogie's orders out of fear, as they are shown cowering over him, and if one talks to Lock before fighting Oogie, he states if they fail, Oogie will no doubt eat them.
All three children wear Halloween costumes with masks. A peculiarity to note is that the hands of the children appear to be different colors than the facial skin underneath and otherwise concealed by their masks. Whether or not they are wearing gloves is unknown.
Lock is dressed as a devil, wearing a plain, long-sleeved, tattered red shirt, and pants of the same color. His brown shoes have pointed toes that curl upward, and he seems to wear pale orange gloves. His skin is an unhealthy grey color, his eyes are an eerie yellow and his lips are sky blue. His upper eyelids are a pink color, while the lower one is periwinkle. His chin is rather large and the top of his head is quite flat.
His ears are set rather low on his head, and his eyebrows are the same shade of red as his clothes, while the rest of his hair is a darker red-brown color. He styles his hair in such a way that he has two "horns" in the front. His nose is pointed, but not nearly as large as Shock's. His mask is a faded red devil's face with horns that curve upward much more than Lock's hair. The mask's mouth is curled into a ghastly smile, showing sharp teeth. Lock's outfit is completed by a red, pointed tail, though it is unclear whether or not this is an accessory.
Shock, the only girl of the group, is the tallest, being only slightly taller than Lock, as well as the thinnest. She is dressed as a witch, wearing a purple witch's hat that is about the same height (perhaps even taller) than her. Her hair is wiry and blue , the same color as the makeup she wears around her eyes. She also seems wear sky blue lipstick (though both Barrel and Lock have lips of the same color, so this may be her normal lip color) and has deathly grey skin, the latter being a trait all three children share.
Her face and neck are quite long and her nose is enormous and pointed, taking up most of her face. Shock's mask is a plain grey-green one that sports the same large nose as her own face, and its mouth is set in a deep frown. She wears a pink dress with a dark purple hem, as well as black boots and dark purple gloves.
Barrel is the shortest and most rotund of the trio, sporting the same pale grey skin and blue lips as his friends. His head is spherical and he has short, pale green hair. His nose is very small when compared to Lock and Shock's, and it is upturned. His eyes are quite close together and appear to be sunken in, though this could just be an illusion created by the dark makeup around them. Barrel dresses up like a skeleton, wearing tattered purple pants and a like-colored shirt. Both of these pieces of clothing are decorated with bones roughly corresponding to their locations in the human body.
Unlike his friends, Barrel doesn't seem to wear gloves, but his feet are oddly shaped, with three toes of the same length. It isn't clear if they are part of his costume or his real feet. His mask is that of a skull; a simple, round, white mask with the mouth being bare teeth set in a wide grin, reflecting the fact that Barrel himself is usually grinning.
In Kingdom Hearts, they steal an artificial heart from Dr. Finkelstein to give to Oogie. They are soon captured, however, without the heart. After their battle, they reluctantly reveal tips on how to defeat Oogie. They leave the mansion afterwards and can be found at the Halloween Town save point since they lost their playhouse.
The mischievous trio appears again in Kingdom Hearts 358/2 Days, repeatedly playing a trick on Roxas. Usually, when Roxas is about to leave Halloween Town, the three will sneak up behind him and yell "Trick or Treat!". When Roxas turns around, they throw a pumpkin bomb at him, which explodes in his face, then run off laughing. Eventually fed up with this, Roxas dodges one of the pumpkin bombs, and engages in a fight with the trio.
In Kingdom Hearts II, it is revealed that they became Dr. Finkelstein's assistants. When they go out to play, they come across Maleficent and tell her of Oogie Boogie's fate. Maleficent revives Oogie and gives them control of the Prison Keeper Heartless as a distraction for Sora and company.
In the second visit, they are blamed for stealing Christmas presents from Santa. In the inevitable chase afterwards, the heroes discover the truth when they tell them about Dr. Finkelstein's Experiment.
Lock, Shock, and Barrel originally appeared in the 1993 movie The Nightmare Before Christmas. In the movie, Jack wants to take over Christmas, so he orders Lock, Shock, and Barrel to kidnap Santa Claus. When the trio manages to do that, they bring Santa to Jack.
Jack tells the three to take Santa to their lair, but they don't listen to him and bring Santa to Oogie Boogie's lair. Shortly after Jack defeats Oogie Boogie and saves Santa, Lock, Shock, and Barrel arrive at Oogie's lair together with the Mayor, whom they have led to the place.
Their names as a whole is derived from wordplay of the phrase "Lock, stock, and barrel", a merism meaning 'everything', which in turn was derived from the components of a musket.