At an eastern European airport last week (in the EU) where I have travelled for work before, the border guard scanned my passport as usual then looked at her screen and spent ages reading the screen. This is typical when the officer hasn't seen a SIS alert before - they are reading what to do for a 'discreet' check. I was then given my passport back and let through the electronic door into baggage hall. About 60 seconds later the officer suddenly comes running out of the back of her booth and asks me to return - I had to go back through the door and to the front of the queue, where he colleague then asked me the 2 mandatory questions 'where are you going to' and 'are you travelling alone'. Luckily I was on my own and no one in the queue that I recognised.
I put this down to the officer not reading her instructions properly.
On the return flight, guess what ... exactly the same thing. Wait, wait, read, read, given the all clear, move through and as heading towards gates young officer comes running to call me back.
As I'm let back through the second time, I rolled my eyes and quietly laugh as I walk to the gates. A big english guy has seen all of this in the queue, follows me through and sees me with a smile on my face. He jokingly asks me in a big booming voice that everyone else nearby hears ' Wow, mate, you had them in a real panic... did they find your really big criminal record ha ha ..'
If I had been travelling with a work colleague could have been a really difficult situation. As it was, a quick one line response killed the conversation 'I guess I should get around to changing my name from Osama'
Moral of the story - be prepared for anything!