I don't personally have an issue with people having a bit of fun while doing their job professionally, but I can see why others are concerned here. Taxpayers are paying a lot of money for people to have very expensive training and then fly around in very expensive aircraft, and comedy callsigns (or willy contrails) aren't a great look. Every man and his dog has access to FR24 these days, so it's going to get out. I know these people are still doing their job professionally, but others will jump to the conclusion that they're just larking around at taxpayers' expense. Maybe save the high jinks for somewhere slightly less public?