I don't have a birthmark

You're area 51 reptillian/human hybrid material.

Do you eat small rodents, mice, guinea pigs for sustenance?

Do you occasionally hiss at passers-by?

Do you like sleeping under heat lamps?

Do you have one of those lizardy forked tongues?

Do you order your take-out/takeaway from Petsmart?

No, yes, no.

Maybe you have a birthmark somewhere you can't see?

Look under your hairline for 666. If it’s not there, you're made out of porcelain so try not to fall.

What is so rare about not having a birthmark? Billions of people don't have one. I would be more impressed if you had said that you were born without a navel. Now that would be an event.