MTV has a new interview with Emma and Rupert where they talk about Quidditch.

“She definitely disagrees with Harry putting the Felix Felicis in Ron’s drink because it’s the equivalent of taking steroids before a match or for athletics,” Watson explained. “She really disagrees with it, but then she finds out that Harry’s actually been smarter than her and it’s all a psychological thing.”  That’s because Harry doesn’t actually put the potion in his drink — Ron just assumes he’s been dosed and thus plays spectacularly. “It’s kind of like a placebo drink,” Watson said. “So it’s all OK in the end.”

For Grint, who plays Harry’s buddy Ron, “Half-Blood Prince” gave the actor his first opportunity to engage in some cinematic Quidditch. “I was actually really gutted last year because that is sort of Ron’s big Quidditch moment and I was really upset they didn’t have that in [‘Order of the Phoenix’],” he said. “I was really looking forward to doing it this time, but it’s actually sort of an anticlimax because it’s really hard work. You’re on a broom for a long time, like a few hours at a go,” Grint grinned. “You’re literally sitting on a broom and it gets a little bit sore down under a bit. It’s been fun, but it’s quite hard work.”