We had an employee (first name Peter) who was dumb enough to fall for a phishing mail and enter his work credentials on the attacker’s website.
To be safe (and honestly, also to teach him a lesson) we deactivated his account and recreated it with a different username and e-mail.
His alias is now p.lastname instead of peter.lastname. A couple weeks later I found out his coworkers now call him Pee-Dot behind his back.