Rowling's books mentioned the games but didn't spell out exactly how Harry and friends play them. Roberts and team dreamed something up. "We wrote the rules up for all these games, sent them off to J. K. Rowling, and she went, 'Yeah, OK, those are the rules,' " he told MTV News during a visit to EA UK's Guildford, England, studio just outside of London. "It's kind of cool. We got to make all the rules."

She has written documents for us, explaining how certain things work, why you shouldn't do certain things that we're not supposed to say because they're secret.

And she has put her foot down when need be. Roberts and the team came up with a mission in the game that would have Harry's classmate Neville Longbottom sabotaging a clock tower to get back at Hogwarts professor Dolores Umbridge. "We got this feedback from her saying, 'I really like the mission, but I don't think Neville would do that. I think it would be Dean Thomas. He's much more likely to do it.' " They switched the mission to Dean.