When Joker is speaking to Gordon over the intercom in Batman: The Killing Joke, the enunciation and rhyming scheme (and the fact that he asks for music) make it pretty obvious that the Joker is singing. Is there an official source on how the song was supposed to be sung? Melody, timing, pitch, etc?
When the world is full of care
And every headline screams despair,
All is rape, starvation, war and life is vile
Then there’s a certain thing I do
Which I shall pass along to you,
That’s always guaranteed to make me smile:
I go loo-oo-oony as a light-bulb battered bug!
Simply loo-oo-oony, sometimes foam and chew the rug!
Mister, life is swell
In a padded cell,
It’ll chase those blues away:
You can trade your gloom
For a rubber room
And injections twice a day!
Just go loo-oo-oony like an acid casualty,
Or a moo-oo-oonie, or a preacher on T.V.
When the human race
Wears an anxious face,
When the bomb hangs overhead,
When your kid turns blue,
It won’t worry you,
You can smile and nod instead.
When you’re loo-oo-oony, then you just don’t give a fig,
Man’s so pu-uu-uny, and the universe so big!
If you hurt inside,
And if life should treat you bad...
Don't get ee-ee-even.
- Batman: The Killing Joke, Alan Moore and Brian Bolland