> *knock*
> Who’s...
> *knock*
> Who’s...
> *knock* *knock*
> Who’s there?
> *knock* *knock* *knock*
> Who...
> *knock* *knock* *knock* *knock* *knock*
> Piss off, Fibonacci!

*knock* *knock* *knock* *knock* *knock* *knock* *knock* *knock*
(Sound of some late 1980s Williams pinball machines at power-on that
detected a bad switch during previous play)