sshd created user, or did i dream?

[dexter2 <dexter2@nextra.sk>]

Hi,
i've instaled Debian GNU/Linux on old machine. I did not create any user
on it, i used just root. Than run sshd on it. On another PC with Debian
i wass loged as normal user. I typed command.
john$ ssh 10.0.0.3
I wass expecting to be asked for username and password, but i wass
prompted only for password. So i typed in, the root password. And by
some miracle i loged in. I typed:
$whoami
john
$cat /etc/passwd
............
..........listing of passwd file........
So user john wass created with root rights. But command completion for
only root commands did not work. Unfortunately id did not try to run
one. Today i erased user john from old machine and tried all againg, but
now it did not work. 
Do somebody understad it? 
Is it feature, that fresh system behave like that. 
Is it a bug? 
Or, did i dream? (it wass allready quite late)
Thanks for explanation.

   Dexter