When you have the following discussion with the AMS officer
"Where did you arrive from"
"USA"
"How long are you staying?"
"about 3hrs"
"Then where are you off to?"
"USA"
and a confused look

Or a multiday back to back MRs where the ground staff know you by name and lets you board with the crew.

or a flight cancellation while waiting in line you got your netbook in one hand with EF open and KVS looking at options, talking to the UA agent in the other over the phone and you get to the front (mind the line is only a few people deep) and you just tell the agent to unload you, print the new BPs, change the bag tags and off you go