'Harry Potter and the Half-Blood Prince' is poised to take the box office throne this weekend, and series stars Daniel Radcliffe, Emma Watson and Rupert Grint reflect on the incredible magic of the series -- and romance, onscreen and off!

"A lot of us now are in kind of quite serious relationships, or have been in relationships for quite a substantial amount of time, so for us to suddenly have to play all the young teenage love stuff is really, really quite good fun," Daniel tells ET.

In the real world, several reports say that Daniel likes to date older women, and he candidly explains to ET, "People think that it's a thing that I have, but actually it was kind of a matter of practicality. Women who are older than me when I was like 17 or 18 would have jobs, normally, so they would understand the idea of me having a job. Whereas if I'm 16 going out with 16-year-olds, they can't quite grasp the fact that I work nights sometimes and I'm not always around. And, also, older women are really cool."

In the new movie, in theaters July 15, hormones are racing among the students of Hogwarts thanks to a powerful love potion. Harry, Ron and Hermione are not immune, as they find themselves drawn to some, avoiding others and grappling with growing jealousy as they prepare to battle the evil Voldemort. For those familiar with the story (spoiler ahead!), Ron and Hermione share a momentous kiss, and Emma says that the set was buzzing the day of their lip lock -- and the producers sent Daniel far away to reduce the tension!

"Everyone wanted to come watch it," says Emma, "and Rupert and I were struggling so much with the pressure anyway -- if Dan had been there it would have been too much, I think."

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