Not a joke as such but this poem cracks my son up every time:
The Spot on My Bum
Good grief! This spot on my bum,
I've squeezed it so much that my cheeks
Have gone numb.
It's big and it's red
With a big yellow top,
I've squeezed it with pliers,
But still it won't pop!
I've soaked it in water,
I've put on some cream.
Mum had a squeeze
Which just made me scream.
I can't sit down now,
The pain is quite dire,
My spot is glowing
And my bum is on fire!
I cried to my mum,
"Just one last try, please!"
So mum, with a grip like Superman,
Started to squeeze.
Yes, mum had hold of my spot
With a vice-like grip,
My eyes they were popping
And I was biting my lip.
My body started shaking without restraint,
My legs they wobbled,
I started to faint.
Then my mum cried out with such distaste
Because my spot, like a time-bomb,
Had exploded in her face!