Who's that weirdo down there? No, don't look... You'll only encourage him!

Anyways... Here's the original...

An Apple A Day

An apple a day

Sends the doctor away

Apple in the morning

Doctor's warning

Roast apple at night

Starves the doctor outright

Eat an apple going to bed

Knock the doctor on the head

Three each day, seven days a week

Ruddy apple, ruddy cheek.

Here's angerbda's way cooler version...

A parsec a day

Ship leaves the Milky Way

Hyperspace boarding,

Black hole warning.

Living long years trice,

Grandpa is in the ice.

Robots on the crew

Keep the cryo stasis through

Ready to warp, faster than light,

Travel sharp, Galactic flight

And here, well...

https://youtu.be/_pTI-k62ndE