With the clock ticking down at the end of extra time and the match goalless, coach Louis van Gaal sent Krul, 26, on as a replacement for first choice keeper Jasper Cillessen.
It proved a shrewd move as the towering Krul saved spot-kicks from Bryan Ruiz and Michael Umana to hand the Dutch a 4-3 victory and a place in the semi-finals against Argentina.
"That is not normal," Krul said. "You sit the whole match on the bench and then you have to go in and save the penalties. I don't know what I can say."
Krul plays his club football at English Premier League side Newcastle United where he is not known as a penalty specialist. He has saved just two of the 20 he has faced.
"You sit on the edge and think it might go to extra time and penalties and you have to take the team from the quarter-finals to the semis," he added. "It's a dream, it's unbelievable."