In the twilight years of the 280s we 'liberated' the IRO's ship crest during a fuel transfer. This was when they dumped old fuel from their water compensated tanks that had questionable daily fuel husbandry into ATH on short notice in an after hours event. We initially left it for the CO on his table, but then never heard anything from IRO asking if we had it.
About a month later we were in Saint John's and decided it would be fun to leave it in safe keeping at the Crow's Nest, and sent them a letter letting them know where it was. IIRC we ended up actually getting one of our crew to pick it up when he went back on holiday, but was pretty funny at the time, and the photo of it sitting behind the bar was pretty legendary. Dumb, but fun at the time.
I'm sure that's pretty tame compared to a lot of the pranks and hijinks those walls could tell though, cool spot with a lot of history.