During the production of the romantic comedy “Dave,” which celebrates its 25th anniversary on Monday, director Ivan Reitman would frequently drop by the editing room to see what editor Sheldon Kahn had assembled.

Reitman had watched about two-thirds of the movie when he realized one scene didn’t work — when Dave (Kevin Kline), a good-natured employment agency owner hired to impersonate the officious President Bill Mitchell after the POTUS suffered a stroke, and the no-nonsense First Lady (Sigourney Weaver) return to the White House after sneaking out.

“I didn’t buy that Sigourney and Dave bonded when they went back into the White House,” Reitman said. “It was just that they snuck out and they talked a bit and then they snuck back. It didn’t feel that they had earned each other’s trust. It was just a movie movement instead of an earned movie moment.”

So they turned it into one of the most charming and funny movie moments in the classic. The film was doing some location shooting in Washington, D.C., when Reitman and screenwriter Gary Ross started discussing the two characters being stopped by traffic cops. “They look like the real things and they are the real things.” But the two tell the cops they are impersonators and break out into “Tomorrow” from the musical “Annie.”

“We just sort of squeezed in an extra day of shooting there,” noted Reitman. “I remember standing — it was around 5 p.m. in the evening. It was getting dark and we were getting ready to shoot the scene and we thought, ‘Tomorrow’ would be a perfect song to sing. It’s the kind of thing that so-called presidential impersonators could do.”

But they didn’t have the rights to the song. Ray Stark, who produced the 1982 film version, owned the rights. “So somehow I got Ray Stark on the telephone. I knew him. I said we’re not making fun of the song. I explained to him in three seconds what the scene was. He said, ‘Okay, but you’re going to owe me, kid.’ It was his favorite line.”

After the film was released, Kline recalled being a passenger in a car with someone who was speeding when two police cars were on the median. Of course, they were pulled over.

The cop recognized him as the star of “Dave” and asked him, “‘Why did you tell the cop who stopped you [you were impersonators]? Why didn’t you say who you were?’ He said, ‘Well, I quite agree with you. It makes no sense, but it’s much more fun to have Sigourney sing ‘Tomorrow.’’ Anyway, my friend did not get a ticket!”

Even a quarter of a century after its release, Kline is constantly being stopped on the street by people who tell him how much they love the film. “Some people just call me Dave,” he quipped.

He recalled walking down the Fifth Avenue during George W. Bush’s presidency when the POTUS was visiting. “There was a police escort,” Kline said. “I was just looking, and someone said, ‘I wish it was you. Why didn’t you run?’’

Former President Barack Obama once told Kline “‘I love ‘Dave.’ I love watching it when I’m depressed because you make it look so fun, you make it so easy.’ I think if our current president saw the movie, he’d be rooting for [President Mitchell].”

Though the basic plot of a lookalike taking over for someone official isn’t anything new — it’s appeared in everything from “Prisoner of Zenda” to Paul Mazursky’s 1988’s “Moon Over Parador” — Ross found “Dave” difficult to write. In fact, Ross, who earned an Oscar nomination for “Dave,” had to ditch his first draft for the film and start over from scratch.

“It’s a deceptively hard movie,” he said in an e-mail interview. “Mainly because the premise is so preposterous. Everyone knows the language of politics and the optics of politics — they see it every day in the media. So, it’s very hard to make a fairy tale real when its set against contemporary politics.”

That’s one reason there were several cameos in the film — including the late Tip O’Neill and Paul Simon — and journalists John McLaughlin and Chris Matthews of “Hardball” were important for the film to succeed.

Reitman, he noted, “deputized me to go to Washington and round up as many [cameos] as I could. So Warner Bros. printed me some business cards with their log on it and I hit the White House Correspondents’ dinner trying to round up cameos. The cameos provided ‘verisimilitude,’” Ross said. “But I also had backed off the political point of view I had in the first draft. I tried to make it too neutral politically. When I committed to Dave’s character owning an employment agency and trying to help people get jobs, the script got much easier to write.”

“Dave,” said Ross, is both a comedy and a political film. “That said, I think it examines the tensions between innocence and corruption, but I suppose that’s present in a lot of my films.”

If Dave is the epitome of goodness and innocence, Frank Langella’s Iago-esque White House chief of staff Bob Alexander is the embodiment of everything evil and corrupt in government. Though Kevin Dunn’s communications director Alan Reed may not be in the same league as Alexander, he still is in cahoots with the chief of staff.

“I can’t say enough about how well Frank Langella played that part,” said Matthews, who is a friend of Ross’. “The way he came in organized and set up his press conference. The way he threw his notebook, his binder on the lectern. Complete confidence. This is his world. He owns his world. Totally at ease in his surroundings and a command of them and used to calling the shots, even with a president around.”

Matthews believes there is a lot of the late Barbara Bush in Weaver’s Ellen Mitchell. “Well, look at her, she’s a very confident woman. Very confident socially. There’s a part of Trump that is Dave, too. He’s so ill-prepared and he’s almost an imposter in and of himself.”

Still, Matthews added, “I do think the idea of this movie is that a good person can be a good president.”

Dunn’s son was born during the film. And he laughed when he noted that Ivan told him jokingly, “Tell you wife to have the baby on a Saturday.” So, she did. Both Dunn and Reitman feel “Dave” would be a far different film if was made in today’s political climate

“I think the political spectrum is so tarnished,” Dunn said. “There’s no dignity to anybody. Everybody kind of falls for it. It’s not confined to Trump. Everyone’s just kind of sunk to his game.”

Reitman purposely put “an innocence” into the film “as a way of trying to capture the kind of thing that Frank Capra did in his day for this period, which is really the 90s. It’s amazing how the world has shifted out of it. It’s much more cynical and an almost impossible place.”

Though it’s hard to envision anyone else but Kline in the film, it was actually Warren Beatty who brought Reitman the project. After working with Beatty and Ross on the script, Reitman told Warner Bros. he thought it would be a great movie.

“They were about to make the deal and they said, ‘We’d rather just do the movie with you, but not Warren.’ I said, ‘I can’t do that. Warren was the one that sent it to me.’ I actually walked away from the movie for about four months.”

The studio eventually called him and said they were going make a deal with Beatty.

“So they made a deal with me and then Warren in his own inimitable way wouldn’t make a deal or they wouldn’t come to terms.”

Because he didn’t respond, Reitman decided to try to get someone else. Beatty, “was very pissed at me for a while, although we’re friendly now. Then of course, I couldn’t get anybody to say yes.” Including Kevin Costner.

Kline also turned down the piece because he thought they wanted him to repeat his Oscar-winning role of the wacky munitions expert in 1988’s “A Fish Called Wanda.”

“I thought he was casting me for all the wrong reasons,” Kline said. “But when we spoke, I knew in 30 seconds he wanted something totally different. We were absolutely on the same page about what it should be because it’s not a farce. It’s very delicate sort of romantic comedy.”

Still, Dunn said, “there was a chance for slapstick comedy in every scene. Everybody was game.”

And, Dunn added, the cast and crew would always try to figure out when Kline would do a pratfall.

“What happened was at rehearsals I was sort of overdoing it a bit when I first sat down in the chair in the Oval Office. And [the chair] falls over. Then Ivan encouraged me to find other places [for pratfalls]. Ivan was wonderful in the way he would let us play and improvise, ad-lib whatever, and just be spontaneous without adhering to the script.”

Reitman, Kline explained, “edited the film to make it as real as possible and not too silly — that perfect balance of comedy and romance against the most cynical background imaginable.”

At the film’s conclusion, Dave is reunited with Ellen and is running for city council.

Would he be a senator now? A governor?

“I think he’s the president by now,” offered Kline. “Certainly.”