Naomi Watts better get on a serious exercise regimen because reports are she has signed on to star in the next ‘Harry Potter’ movie. The pregnant Mulholland Dr. star, 38 – who will give birth in August will play Draco Malfoy’s wicked mother Narcissa in Harry Potter and the Half-Blood Prince, the sixth movie in the fantasy franchise.

The film is currently in pre-production but is expected to hit cinemas in November 2008. The latest of the boy wizard movies to be released, Harry Potter and the Order of the Phoenix, has already given Warner Brothers bosses their biggest opening ever, taking $561 million worldwide in its opening 12 days earlier this month.

UPDATE: Mtv.com is reporting that Naomi Watt’s reps are already saying this is not the case. “Not true,” declared representatives for Naomi Watts. I guess they didn’t think she could lose that baby weight after all.

Source: pr-inside