College coach trip
On a college-organised coach trip to Amsterdam, we were arriving at Dover when two of our party realised that they had forgotten their passports. Instead of heading back to London to fetch them, our tutor insisted that we carry on regardless and hope for the best. At every border check the two students in question wedged themselves into the footwells while we covered them with coats and bags.

We were instructed to be as loud and annoying as possible when the officials came. It worked every time - when faced with a coach load of rowdy and obnoxious British teenagers, the checkpoint staff were so keen to get rid of us that they waved us straight through. So we successfully smuggled two people in and out of several countries. On the way back I'm pretty sure that wasn't the only illegal cargo we had...
(Supermonkey, Sun 17 Jul 2011, 2:17, Reply)