My favourites are from Monty Python;

A Short Poem

Po.

Horace

Much to his Mum and Dad's dismay
Horace ate himself one day.
He didn't stop to say his grace,
He just sat down and ate his face.
"We can't have this his Dad declared,
"If that lad's ate, he should be shared."
But even as he spoke they saw
Horace eating more and more:
First his legs and then his thighs,
His arms, his nose, his hair, his eyes...
"Stop him someone!" Mother cried
"Those eyeballs would be better fried!"
But all too late, for they were gone,
And he had started on his dong...
"Oh! foolish child!" the father mourns
"You could have deep-fried that with prawns,
Some parsley and some tartar sauce..."
But H. was on his second course:
His liver and his lights and lung,
His ears, his neck, his chin, his tongue;
"To think I raised him from the cot
And now he's going to scoff the lot!"
His Mother cried: "What shall we do?
What's left won't even make a stew..."
And as she wept, her son was seen
To eat his head, his heart, his spleen.
And there he lay: a boy no more,
Just a stomach, on the floor...
None the less, since it was his
They ate it - that's what haggis is.

This next one isn't really a poem, more of a song;

Lumberjack Song

I'm a lumberjack
And I'm O.K.
I sleep all night
And I work all day.

I cut down trees
I eat my lunch
I go to the lavatory
On Wednesday I go shopping
And have buttered scones for tea.

I cut down trees
I skip and jump
I like to press wild flowers
I put on women's clothing
And hang around in bars.

I cut down trees
I wear high heels
Suspenders and a bra
I wish I'd been a girlie
Just like my dear Pappa.