I choose a Bobby McFerrin song: Don't Worry, Be Happy. I think is very famous, don't you?
Here is a little song I wrote
You might want to sing it note for note
Don't worry be happy
In every life we have some trouble
When you worry you make it double
Don't worry, be happy......
Ain't got no place to lay your head
Somebody came and took your bed
Don't worry, be happy
The land lord say your rent is late
He may have to litigate
Don't worry, be happy
....
Well, is only a piece of the song
:-)