Answer:
A darkΒ-colored creature serenaded by Lennon and McCartney.
What peels like an onion but still remains whole?
Slithery critters with a taste for dirt.
It can be white or blue or black, Humped or have a horn. And when it talks it sings its menuets, as it's travelling the depths.
The strangest creature you'll ever find: Two eyes in front and many many more behind.
I repeat only the last word you say. The more I repeat, the softer I got. I cannot be seen but can be heard. What am I?