This was the highest-grossing movie of 1987 in the United States.

During the two week rehearsal period before filming began, then-bachelors Tom Selleck and Steve Guttenberg took the long-married Ted Danson out on the town with them, visiting a few Toronto night clubs, bars, and restaurants, to rekindle the feeling of bachelorhood they had to project in the film. The three caused a lot of excitement among the public whenever they went out to party.

When Jack's mother comes to visit Mary (Lisa Blair), you can see in the background what appeared to be a little boy standing in a doorway. There is a rumor that this is the ghost of a little boy who died in the apartment in which the film was shot. This rumor is false, as the interiors were all shot on a soundstage in a movie studio. The "ghost" is actually a cardboard cut-out of Jack wearing a tuxedo. This prop appeared later in the movie, when Mary's mother comes to collect her.

Director Leonard Nimoy had some arguments and differences on the set with the lead actors. According to Steve Guttenberg, Tom Selleck and Ted Danson were used to being the bosses on their own television shows, but soon learned that the real boss in charge was Nimoy. Guttenberg said, "Leonard was a good director, and being an actor, he knew the problems actors face, although sometimes I think he forgot."

The Pampers Company paid $50,000 for their brand of diapers to be used in the film.

Factual errors

When Peter and Michael are trapped in the elevator at the construction site because of Jack. Peter is shouting to hit the button on the left but to turn on and off the elevator are switches.

The name "Jan Clopatz" doesn't even remotely sound Hungarian. "Jan" is a male given name (version of "John") used, among others, in the German, Polish, Czech, Slovakian, Dutch, and Croatian languages, but not in Hungarian, where the common form of "John" is "J?nos". The surname "Clopatz" is complete gibberish. Also, the character (played by Dutch actor Derek de Lint) speaks with an accent which doesn't sound Hungarian at all.



Incorrectly regarded as goofs

When Jack's mother comes to visit Mary, you can see in the background what appears to be a little boy standing in front of a window. There is a rumor that this is the ghost of a little boy who died in the apartment in which the film was shot. This rumor is false, as the interiors were all shot on a sound stage in a movie studio. The "ghost" is actually a cardboard cut-out of Jack wearing a tuxedo. This prop appears later in the film, when Mary's mother comes to collect her. Some argue that "it's smaller" or "it's dressed differently", but close examination reveals that it really is the cardboard prop.



Revealing mistakes

When the bad guys are in the elevator, Vince says to Satch, "Doesn't this thing go any faster?" But the background is not moving in accordance to the elevator.

In the same scene when Jacks mother comes to visit Mary, when she walks past the sofa to the right there is a prop of a rifle standing on end right behind the sofa as they walk across the room. When they walk back across the room to the left, the cardboard cutout is in the window.

When Colin Quinn who plays a gift clerk opens the register you can see that it is empty but somehow he gives back three dollar's to the customer.

When Colin Quinn who plays a gift clerk opens the register to put a five dollar bill into it instead of putting it to into the second spot to the left he puts it in the same spot where 1 dollar bills are supposed to be in.



Character error

When the guys are trying to convince Sylvia to stay with them and talking over each other, Ted Danson calls her "Cynthia".

After Peter and Michael left the show early to check on Jack and Mary (after repeatedly not getting any answers by phone), Peter says to Jack, "I let the phone ring for five minutes..." However, the answering machine would have picked up after two or three rings.

When Michael says Gabby Hayes had no teeth and he was 90 the age was wrong. Gabby Hayes lived to be 83 years old.