I think my favorite would have to be either "Clarence" (who bought a brand new maw and a better paw) or...
Stung by a Bee
by Shel Silverstein
I got stung by a bee
I can't tell you where
I got stung by a bee
It was just lying there
And it tatooed a message
That I can't let you see
But it spells out....
'Hello, you've been stung by a bee.'
I love that it was 'spelled out' in the pic on somone's cartoon bottom!