As I've discussed elsewhere online, I've had more than a few experiences with coworkers discovering that I'm ticklish and then periodically attacking me in the workplace, an experience which has always been equal parts fun and panicky. No reason to believe any of them were more than just playful mischief-makers who were happy to have stumbled onto my particular weakness, though one of them was a little more committed to tickling me than the others, and I'd seen her occasionally try tickling other coworkers or asking if they were ticklish, so she may have been a little more focused on it than the others.
All those folks have moved on now and I haven't gotten tickled in the office in quite a while, though. I wonder if it's because the wider workplace climate has changed.