An English version of the one Azizi posted at 09.02pm
My friend Billy had a 6 foot willy
And he showed it to the girl next door
She thought it was a snake and she hit it with a rake
And now it's only 5 foot 4
(of course I didn't know what it meant, when I heard it at school!)

"I'm Being Swallowed by a Boa Constrictor".
I'm Being Swallowed by a Boa Constrictor and I don't like it one bit (twice)
Oh no, its up to my toe (twice)
I'm being...
Oh gee it's up to my knee
Oh fiddle, it's up to my middle
You've guessed, it's up to my chest
Oh heck, it's up to my neck
Scream
Ther may be more, that's all I can remember. I heard it at a Hobby Horse club at Litchfield Folk Festival about 10 years ago.

Then of course there's the tune called Morgan Rattler.