the longest one I know is
There was a thousand -legged worm and he began to squirm
"Has anybody seen a leg of mine?"
If it can't be found I'll have to look around for the other ninehundred ninety-nine
Look around, look around, for the other 999
If it can't be found I'll have to look around for the other ninehundred ninety-nine

There was a thousand -legged worm and he began to squirm
"Has anybody seen a leg of mine?"
If it can't be found I'll have to look around for the other ninehundred ninety-eight
Look around, look around, for the other 998
If it can't be found I'll have to look around for the other ninehundred ninety-eight
[and so on]...