For Americans you also need to get finger prints for the FBI check they now require. I know someone who has gotten that done at are local police station and sent it back home for the check.
I think the OP is referring to the fact that immi offices take an optical scan of your prints, which they must now do.
In 2012 will foreigners need to stand one leg and touch their fingers to their noses at the airport? Tune in next year for the next exciting episode of Korean immigration!
In all seriousness, it's no big deal and the people I've had are really chill. Not true for Mokdong. Overworked and cranky they are. Though it can work to your advantage if they stamp whatever incomplete paperwork you have to make you go away. Then again you are more easily rebuffed. It's a toss up. I recommend going on Friday right after lunch.