A classic Walt Disney cartoon featured dancing skeletons and animated skeletons often appear in cartoon features.  Such skeletons not only dance, but trade heads, fall into piles of bones, and reform into skeletons again.  This skeleton variation called dry bones is inspired by the antics of cartoon skeletons.  The name comes from the song of the same name ("the leg bone's connected to the hip bone," etc).

Dry Bones (skeleton variant)
Medium Undead
Hit Dice: 4d12 (29 hp)
Initiative: +5 (+4 Dex, +4 improved Initiative)
Speed: 30 ft
AC: 16 (+4 Dex, +2 natural)
Attacks: 2 Claws +2 melee
Damage: Claw 1d4
Face/Reach: 5 ft x 5ft/ 5 ft
Special Attacks: Feign Destruction
Special Qualities: Undead, Immunities
Saves: Fort +0, Ref +1, Will +2
Abilities: Str 10, Dex 18, Con - Int -, Wis 10, Cha 8
Skills: Perform (dance) +8
Feats: Improved Initiative
Climate/Terrain: Any land and underground
Organization: Solitary, Any
Challenge Rating: 2 
Treasure: None
Alignment: Neutral 
Advancement: --

Dry bones often masquerade as piles of old bones, being able to dismember themselves at will until they are destroyed. 

Combat
     Feign destruction (Su):  A dry bones taking 10 or more hitpoints or more in damage collapses into a pile of bones.  After one round, the bones reform into a skeleton and attack again.  The process continues until the dry bones lose all of their hit points, at which the dry bones falls apart forever.
     Undead:  Immune to mind-influencing effects, poison, sleep, paralysis, stunning, and disease.  Not subject to critical hits, subdual damage, ability damage, energy drain, or death from massive damage.
     Immunities: Bloody bones have cold immunity.  Because they lack flesh or internal organs, they only take half damage from slashing or piercing weapons.

Monster converted from first edition version presented in the October 1988 issue of Dragon Magazine in the article "The Ungrateful Dead" by Tom Moldvay.