In case you don't know: Bambam is a HUGE GD fan boy.
So basically he was on M!Countdown and got to meet Big Bang. He admitted his was a huge BB fan, but suddenly Daesung was like 'oh really? cause i found something you wrote...'
It turns out Bambam had written a letter to GD and it said that it's because of GD that he became a performer and he thanked him so much.