Had an office stalker. She started sending emails from anon addresses but English isn't her first language and it was very obvious. I started to get extra freaked out when she started sending postal messages, not sure why, maybe because that's "more effort".

While doing all that, she would constantly call me and either act normal or slightly flirty, thinking I hadn't figured out it was her writing the anonymous emails and letters. Playing along, I made it really clear several times I had a girlfriend and she finally backed off. But every year for several after that she would email me on my birthday and tell me stuff like "Even though you're older you're still young to me."

She moved to a different job site but she didn't get moved to the correct email group so she was still getting our building-wide announcements. One time I emailed everyone to let them know there was halloween candy near my office. She replied back to me that she hoped I would save some candy for her. The final sentence was "I am waiting for your candy."