Liar, liar, pants on fire

Screamed by little children at one another in the playground, and is presumably a rudimentary accusation technique.

The connection between lying and burning pants is not entirely clear, as cases of spontaneous human combustion aren't generally linked to pathological liars as this remark would suggest. I suppose variants such as "Liar, liar, nose is growing and is made of wood" lack the compactness and style that makes this particular remark so popular.

One expansion of this saying common when I was in grade school was "Liar, liar, pants on fire, hanging from the telephone wire!" Besides adding a (moderately awkward) rhyme, this version extends the discomfort associated with lying: not only are the liar's pants alleged to be undergoing combustion, but s/he is also suspended several meters above the ground by them. Presumably, the result is one hell of a wedgie.