fatty and thinny
[examples] Two subjects of a perpetually expanding song. The pattern of comedy would follow the Little and Large model, wherein Fatty would fart or do something amusing, and Thinny would either suffer, or not be involved. Thinny never got the laughs, and probably fantasised about Fatty's death in many different ways - if my understanding of murder motives is correct.
written by Jo* B*yt*, Jo*Denh*m, approved by Log

A freindly version;
Fatty and Thinny were in the bath,
Fatty blew off and Thinny laughed.
And a recent ad lib by a friend;
Fatty and Thinny were in the hay,
Fatty blew off and Thinny was gay.
written by Ha*ry N*ce, approved by Log

Fatty and Thinny went to the loo,
Fatty did wee wee and Thinny did poo.
written by Ro* J*hnson, approved by Phil

Fatty and Thinny went to the zoo,
Fatty liked monkeys and skinny did too.
written by Ro* Jo*nson, approved by Susan

Also refered to as Fatty & Skinny. This didn't really effect the meter or maturity of the rhymes, as this couplet demonstrates.
Fatty & Skinny went up in a rocket,
Fatty came down with shit in his pocket.
written by Ma*ky *ark, approved by Log

And for the children whose brainpower was in constant battle with tartrazine-fuelled hyperactivity...
Fatty and thinny went on a hunt,
Fatty's a fat cunt and thinny's a fucking twat.
written by Ro* Mars*, approved by Log