Good one. Thanks for bringing this one to light.
I was once putting together a report for a college class. I was writing the report as part of a group, and my assignment was to write my section and put it together with their sections in the whole report.
One of my group members handed me his section of the report, and in it was the word "theyself." For example, "This design allows one person to perform the task by theyself."
I almost choked.
"This design allows one person to perform the task by theyself."
My keyboard thanks you for the coffee shower it just got due to your post.