Funny, I was thinking of this today and thinking I should teach it to the little girls next door!
The song I remember was about 'Jerry'; not Johnny.

All alone for a loaf of bread, all alone went Jerry
Watch the signal, his Mother said; yes, answered Jerry.
but he forgot what his Mother said, and he forgot the light was red,
He felt a big bump and he thought he was dead,
Poor little Jerry.

They carried him home and they put him to bed,
Poor little Jerry.
You're lucky you're living, the Doctor said. Yes, answered Jerry,
They bandaged his leg, they bandaged his head, I'll never do that again, he said.
I'll always watch when the light is red.
Wise little Jerry.