Rivalries, Real, Cartoon, Sports of all sorts, what ya have.
I'm the IT guy where I work.
For some reason, a few people address me by my first and last name when they see me or have a question.
One of them is the facilities/cleaning manager.
One day, I was particularly irritated and before she could get it out, I quickly blurted out both her first and last names.
Since then, we have had a friendly contest going to see who can say the other's first and last name quickest upon sight.
It's been interesting. We keep casual score and have some basic rules.