These are the modified versions of two nursery rhymes (modified by me, of course :P), which were a part of our assginments at the Creative Writing workshop that I'd recently attended. =)
In the first one, we had to keep the first line intact and change the next three lines of the verse.
1. Humpty Dumpty
Humpty dumpty sat on a wall
While he thought of playing football
Humpty won the first game he played
"Oh!", he thought, "My day is made'.
In the second one, we had to keep the entire first verse intact and change the second verse.
2. Jack and Jill
Jack and Jill went up the hill
To fetch a pail of water
Jack fell down and broke his crown
And Jill came tumbling after
Jack and Jill went up again
To teach the hill a lesson
Jack sat down which made him frown
'Cos his pain would still not lessen.