The worms crawl in the worms crawl out.

There are many variations, we like this one.

Did you ever think as the hearse goes by,
that you may be the next to die?
They wrap you up in a nice white sheet,
right from your head down to your feet.
They put you in a big black box,
and cover you up with dirt and rocks.
And all goes well for about a week,
but then your coffin starts to leak.
The worms crawl in, the worms crawl out,
the worms play pinochle on your snout.
They eat your eyes, they eat your nose,
they eat the jelly between your toes.
A big green worm with rolling eyes,
crawls in your nostrils and out your eyes.
Your stomach turns a slimy green,
and pus pours out like whipping cream.
You spread on a slice of bread,
and that’s what you eat when you are dead.