I had a similar but more well managed situation on April 1st this year on an EZY flight from East Midlands to Schipol. Upon landing we were greeted with the usual 'welcome to ......... blah, blah, blah' speech from the cockpit but this time it was a little different when the captain or FO explained that due to fog at Schipol we'd diverted to Rotterdam. Cue lots of concerned looks on the faces of fellow passengers but before anyone had really had much chance to think of the consequences the PA crackled back into life with a merry 'and for those who had previously not noticed today's date is April 1st, welcome to Schipol.'