LSB

LSB is the friendship between Lock, Shock and Barrel from The Nightmare Before Christmas fandom.

Canon
Lock, Shock and Barrel are a trio of trick-or-treaters living on the outskirts of Halloween Town. At some point before the events of the movie, they became associated with the notorious Oogie Boogie. It had gotten to the point where even the Mayor of Halloween Town warns Jack Skellington of the arrival of "Boogie's Boys" (though Shock is a girl) when he assigns every citizen of Halloween Town a task for this year's first Christmas celebration. Jack however is very tolerant of their presence, tells them the task of taking Santa Claus (or "Sandy Claws") to him by force, bribing them with candy should they succeed. However, Jack does not trust Oogie Boogie and explicitly forbids them from telling him his plan. They all cross their fingers behind their backs.

Though despite Jack only telling them to kidnap him, the three kids have a discussion of all the sadistic things they could do to him once they got him. They loudly sing about these plans, making Oogie Boogie aware of them. However, when Lock and Barrel make plans to outright blow him up, Shock tells them off. Not because of any moral obligations, more because she is scared that they will "lose some pieces", with her telling them how furious Jack will be when he asked for a full Santa. During their singing session, they also talk about how much they expect a reward of Oogie Boogie and how they'd hate to be on his bad side. Eventually, Shock manages to come up with a foolproof plan that involves luring Santa away with a present, then bagging him. So they set out on their wind-up bathtub to the trees leading to other holiday towns, sure that they'll get Santa easily.

So of course they mess up. When they arrive at Halloween Town Hall to present "Santa" to Jack, a pink bunny hops out out of their bag. Though none of them can identify the hare, the sash around his back reads "Happy Easter". Jack is not too happy with the mishap, telling them that there's more than just one door and shows them a cookie shaped like a Christmas tree to show them what the right one looks like. When they still expect a reward for bringing the wrong guy, Jack makes a scary face to convince them to get the real Santa. He apologizes to the Easter Bunny and tells the trio to bring him back where they got him first.

Eventually, just in time for Christmas Eve, the trio does manage to bag Santa like they planned and present him to Jack, who is more than satisfied and tells Santa that he'll take over for this year. He then tells the trio to hide him where he won't be able to interrupt Jack's ride. So the trio bring him to their home and shove them down the very pipe they use to communicate with Oogie Boogie. However, when Sally and later Jack, who was presumed to have died on Earth after causing chaos with his Halloween-themed presents, both come to Oogie Boogie's lair to save Santa, the trio is absent when they enter. When the freed Santa crushes Oogie's remains with his boots, the trio is more than happy to see Jack alive and Oogie defeated.

Fanon
Lock, Shock and Barrel are very popular among fans of the movie, largely because they add a lot of fuel for canon-compliant content starring children. They often have theories surrounding their nature as they look more like normal humans than other Halloween Town citizens, leading to some fans believing that they are regular kids who somehow ended up in Halloween Town.

Some people do ship them in a poly relationship, but they are often deemed too young for that.

Fandom

 * FAN FICTION