I brought in some food for a colleague's birthday; it was one ending in 0 so a big one. Our teams all had lunch together that day and another colleague brought a cake. It was a nice event, with a bit of team building for two teams that worked closely together on an important project. The next day, a woman I had never really spoken to (different department, different floor of the building) sent me an email stating that she turned 40 in two weeks and she wanted her lunch catered by Maggiano's. I ignored the message as I thought it was a joke. I was out of the office on leave on her birthday and returned to a bunch of emails, voicemails, and a note on my desk that I was a horrible person for not providing lunch for her "important day". I took pictures of the note and saved her messages. HR called me later in the day to say that she filed a complaint against me for creating a hostile work environment. I explained the situation and they told her to pound sand.