>I heard it was a pair who, on check in, confessed to having forgotten to get a callsign. They were told to adopt the callsign Stupid One and Stupid Two.<
Not wholly apocryphal -- I heard the leader of an A10 pair on handover to London Mil in about 1989 confess to forgetting his callsign. The aircraft were told to adopt the callsigns 'Dummy One' and 'Dummy Two' which they duly did. I had the distinct impression that the penny didn't drop.