While the child actors of Harry Potter have been with us for every film, there's an equally important group of people behind-the-scenes from the very start. Producer David Heyman was the man who first saw some potential in a book by a first-time author; David Barron, who came on board with "Chamber of Secrets," was the more experienced of the two. Speaking in New York, the two gave plenty of insight into the secrets of the films -- and the pains and pleasures of wrapping the series.

On what things kept the "Potter" leads level-headed during 10 years of fame and filming:

Heyman: I think first I count their parents; I think that's key. Also, we had the privilege of making these films in Leavesden Studios, which were a little ... dank. It certainly wasn't a grand place, so it was a little isolated. We had a lot of the same crew working on the films from 2000 right up until 2010, when we finished shooting the films. There was a great consistency in terms of the people, so nobody could get away with anything. If anybody got high on their horse, we'd sure as hell hear about it. It's a great atmosphere; it's a film of great pride but no ego. I think that encouraged a sense of humility on their part, which is one of the qualities I really respect they've retained. They're also surrounded by actors who are at the top of their game who they could learn from, but also saw how they behaved. You had Michael Gambon and Gary Oldman and Imelda Staunton and Ralph Fiennes. They're regular people; they're not a**holes -- excuse my language. They're really lovely, and I think they saw that and they learned from that and they retained their humility and their decency.

Barron: When we started, they were very, very young. The environment had to be one that we could all look at ourselves in the mirror in the morning and feel we were doing the very best we could for children. They weren't some actors, they weren't adults -- they were literally children. They set the tone for the rest of the proceedings. It was a safe place, a friendly place, and there was no ego, as David said.

Heyman: I also think that we tried to keep it fun. Nobody treated anybody like a star. Sure, they each had their dresser and things that you and I may not have on a daily basis, though I probably could use one. They were treated as they were Dan and Rupert and Emma, and everybody's treated with respect, but not fawned over.

On the last day on set:

Barron:  We actually had several last days on set. We had the main unit last day, and then we had inserts and things, but the main unit day was incredibly emotional. We scheduled something very easy for the cast. It was not at all dramatic: It was from the previous film, from 'Part I,' where they were diving into the fireplace and making their escape from the Ministry of Magic. They were on the green stage diving onto a green mattress, so it's not too demanding in terms of their emotional acting range. We were finishing at lunch time because Dan was coming to New York to present a Tony the following day, and we did it: we finished

 I can’t seem to drive two blocks in Los Angeles these days without being confronted with one of the billboards for “The Change-Up,” the new Jason Bateman-Ryan Reynolds body-switching movie opening on August 5. No, I haven’t had a sneak peek at the film, which is directed by David Dobkin (“Wedding Crashers”) and written by “Hangover” writers Jon Lucas and Scott Moore, but that doesn’t stop me from fuming about its ad campaign.

You know the story, right? Jason Bateman, harried husband and father of two young tots, and Ryan Reynolds, hunky single guy who scores big with the babes, have a moment of envying each other’s life while peeing in front of some kind of enchanted fountain (what, you don’t pee in public fountains with your buddies?). Faster than you can say “Freaky Friday,” the two men find themselves transported into each other’s bodies and lives. This overused premise has practically spawned its own genre, with films like “Big,” “Vice Versa,” “17 Again,” “Like Father, Like Son,” “All of Me,” “Prelude to a Kiss,” and, of course, not one but two versions of the Disney classic, “Freaky Friday.” Most of these films involve switcheroos between adults and children but “The Change-Up” posits a grass-is-always-gree​ner scenario between two adult males.

In truth, I have no problem with another body-swap film. It may not be new territory but it’s a tried-and-true scenario that often provides a lot of funny opportunities for its fish-out-of-water stars. No, my only pre-release beef with the film is the underlying assumption present in the billboards, print ads, and trailers I’ve seen for the film (there is so much promotion for “The Change-Up,” Universal must be hoping that this will be their Big Summer Hit once wizard fatigue sets in). Whatever warm fuzzies that exist in the actual screenplay regarding how we should all be grateful for our lives and the people who love us, the ad campaign has one message only: marriage and kids = misery, gross-outs, and indentured servitude while unencumbered single man’s life = heaven on earth. Really?

I hope I don't seem like Michele Bachmann here. I do have a sense of humor, I swear, and I like raunch as much as the next guy (I loved the original “Hangover” as well as “Bridesmaids”). But constantly having to stare down Ryan Reynold’s self-satisfied mug (who’s really Jason Bateman suddenly finding himself single) as he’s surrounded by thong-wearing hotties makes me want to hurl. And seeing Jason Bateman’s “oh crap, why am I alive?” shrug (who’s really Ryan Reynolds suddenly encumbered with the ball and chain) makes me want to come out of the closet as a very happily married man who vastly prefers my life with my wife and two children (one of whom is still in diapers) over the supposed “fantasy” of having wild sex with a different woman every night. Yuck.

Am I being humorless here? Probably, and I do plan on seeing the actual film which may well be very funny (especially with Jason Bateman in the lead). But I remain offended at the taken-for-granted notion that most married people wish they could go back to dating and the single life. To be honest, I can’t think of anything I’d want less! And I wonder if “Sexiest Man Alive” Ryan Reynolds, whose divorce from Scarlett Johansson was just finalized a few weeks ago, might agree with me.