"The movies' lovable sorcerers Daniel Radcliffe, Emma Watson, and Rupert Grint are all teenagers (aged 15-17), so it's no surprise that they deal with occasional bouts of acne. But, according to an onset source, the problem got so bad during the filming of Harry Potter and the Goblet of Fire that the actors' faces had to be digitally retouched in post-production editing! "We had to hire a special effects man," says the source. "He went through every frame clearing up their complexions. " Now that's what we call Hollywood magic!"
Well ... what can you say everybody has it, I don't know if they really needed to clean it up though, unless when they started it wasn't a problem and then they developed it.
A little off topic here, do you guys ever read the "Goofs" section on IMDb? there are only 3 so far for GOF. http://www.imdb.com/title/tt0330373/goofs Check it out.