I ran a BBS in college. And the software I used would allow people to log in via user number, rather than their name if they wanted to. Most people signed in with their number.
I also gave most of the regulars admin privileges, which would allow them to create new forums. So, while on vacation, I came back and found something like 200 new forums, when we normally had like a dozen or so.
So, to get back at all of them, I changed their handles.
When they signed in, it would say something like:
: 72
Are you die_kluge?
Y/N :
And then you'd hit yes, and you'd be logged in. Assuming your password was right of course. So, I changed their names to things like:
A blithering idiot
A complete doofus
A real butthead
So, it would say:
Are you A blithering idiot?
Y/N
And of course, you had to answer yes to get into the system!