Harry Potter's body is changing in new and exciting ways.

With this weekend's release of "Harry Potter and the Goblet of Fire," moviegoers are set to experience a more complicated, more mature boy wizard — who has started to shoot nervous glances at the girls.

"In Book Four, Harry does decide he likes a girl, but it's not Hermione or Ginny," author J.K. Rowling told Scholastic in 2000 when the "Goblet of Fire" book was released. "However, he's only 14, so there's plenty of time for him to change his mind."

Audiences are not the only witnesses to the Potter clan's voyage through puberty. The young actors say it's been pretty strange having to sit back and watch themselves grow up on film.

"I'd be a bit embarrassed to go back and watch it [the first "Potter" film] now," lead actor Daniel Radcliffe, 16, told FOX News. "Hopefully I've come quite a long way since doing that first one."

"So strange. I mean, I was clicking through the channels the other day and 'Harry Potter and the Philosopher's Stone' [the first film's name in England] was playing," said Emma Watson, 15, who plays Hermione Granger. "I just thought to myself, 'oh, my God, I can't believe that's me.'"

But are family movie audiences ready for a girl-crazy Harry?

Greensboro, N.C., mother Mary McGinley, who has read all of the books along with her kids, said Harry's interest in the opposite sex is only a natural side-effect of his aging, and the story wouldn't be believable any other way.

"Harry is getting older," McGinley said. "If he weren't having some sexual, 'girl-crazy' behaviors, I'm sure he wouldn't be accepted as a real teenager by readers. His behaviors are appropriate for his age."

But McGinley also feels that as Harry grows up, he is outgrowing some of the youngest movie viewers.

"As Harry gets older, his experiences, and therefore the movie's intensity, get more serious. This movie is rated PG-13 and parents should take caution with younger children. There are some very frightening scenes in this book," she said. "It will have to be a personal decision for parents of younger children whether or not they can handle the more advanced themes within this book/movie."

The film is certainly the darkest so far. The first to earn a PG-13 rating, the movie ratchets up the violence and frightening imagery to match a much more terrifying, adult plotline in the book.

Eighth-grade Potter fans at Discovery Middle School in Alexandria, Minn., said Harry's growing interest in girls goes perfectly with the darker, more mature turn in Rowling's story.

"Ron and Hermione will end up together. Harry will end up dead," Paul Yager told FOXNews.com.

"I think it will greatly change the story. I mean, Harry won't be the same goodie-goodie we all know," Yager's classmate Luke Boelter added. "He will start to use magic to mess up relationships and get other girls to like him. Also, he will not concentrate as much on his schoolwork, which means he will get in more trouble than usual."

However, some of the kids feared that Harry's dabbling with romance could divert attention from the action and adventure they have come to expect from the movies.

"I'm not sure I like it because it may distract from the real action and magic stuff," student Chris Sletto said.

Authors who have written about Rowling's work say Harry was always meant to grow up with his audience.

"Rowling has always been very clear that she wants the characters to age realistically in the books, and Harry certainly does start to notice the Ravenclaw seeker Cho Chang [played by Katie Leung] in 'The Goblet of Fire,'" said Lisa Hopkins, author of "Screening the Gothic," which looks at the popularity of the occult in film.

"The end of 'The Goblet of Fire' is very dark," she added. "I think Rowling envisaged a large part of her readership growing up at around the same rate as Harry does, and children who were quite young when they first read 'Harry Potter and the Philosopher's Stone' [the first book's title in the U.K.] would probably have been able to cope with 'Harry Potter and the Goblet of Fire.' Younger children might well be frightened, though."

Movie audiences had better get used to a rapidly maturing boy wizard — because the actors are getting older faster than the characters in the books.

"Daniel R. has been a 'sex symbol' to girls of his age from the start, and will continue to be so," said Andrew Blake, author of "The Irresistible Rise of Harry Potter."

"If the movies are to appeal to teenagers as well as 'families,' Harry et al are going to have to be represented as A) having reasonably attractive bodies and B) going through the normal hormonal interest in sex," he added.

"I think this is a real problem for Warner, as it has been for Rowling, who from the start took the decision that this was going to be a series about growing up, not repeated adventures in pre-adolescence."

One sign of just how different a Harry audiences can expect this time around is the appearance on the Internet of a video still of Radcliffe shirtless in the bath in a scene from the movie (which McGinley dismisses as a very non-sexual illustration of a plot point in the book).

And as for the "sex symbol" actor playing Harry, has he received any bizarre overtures from female fans?

He actually got a marriage proposal at Saturday night's "Goblet of Fire" premiere in New York City — and then there was the infamous "towel girl."

"I was doing MTV in New York. And it was freezing cold out. I mean, it's not like it was a warm summer's day. It was so cold," Radcliffe said in an interview with Warner Bros.

"And I got up and they took me over to the window. And there was a girl standing down there wearing nothing but a Harry Potter towel with a sign that said: 'It doesn't get much better than this.'"