A fan was from the US and Junsu went "From! From! Where are you from!" Which Yoochun found hilarious and to that Junsu said 'You don't need to say "Where are you from", you just need to say FROM!" so Yoochun said 'but it should be "from?" With a question tone but you said FROM!"
Yoochun said he will remember this "FROM!", made a deep impression on him (c)