The Two Guys Deli is not a real bodega, it was made for the movie. Yet, in real life people would try to come in and buy things and the production almost got a citation from the city inspector for selling cigarettes without the tax stamps as he didn't realize it was just a set. The name probably came from the TV show Ryan Reynolds was in Two Guys a Girl and a Pizza Place.

When Will and April are talking after he leaves his birthday party he mentions the song "Come As You Are" by Nirvana. Will says the line from the song is "as a friend, as a known enemy", April corrects him saying it's "as a friend, as an old memory." The actual lyric is "As a friend, as an old enemy."

Rachel Weisz was originally set to play the part of Emily.

When doing publicity for the movie, Ryan Reynolds went on Regis and Kelly with guest host Neil Patrick Harris. Because of Harris' involvement in How I Met Your Mother (2005) Reynolds tried really hard not to say that phrase while describing the movie.

Out of the four leads in the film, only Elizabeth Banks is American. Ryan Reynolds, Rachel Weisz and Isla Fisher respectively are Canadian, British and Australian.

Continuity

When Will is asked to get people to attend the dinner for donations his boss says it's on Monday night, but on the phone Will says that its on Thursday night.

When Will and April are smoking outside Two Guys, April's cigarette constantly switches from her right to her left hand depending on camera angle [facing her, left hand; facing Will, right hand]. Same thing with her hair in her apartment on the couch with her hair [framing the left side of her face, framing the right].

Will is sitting outside a small restaurant. Just before Summer's surprise reappearance, the waitress serves him his wine and asks him if he has made up his mind yet. At his place is a sandwich with fries etc., just barely started.

During the scene where Maya convinces Will to tell about his past relationships, her braid switches from being on her shoulder to hanging down her back in between shots.

When Will prepares to leave Madison, Wisconsin, after the New Year's celebration, there's green and full foliage on the trees. Highly unlikely in January 1992, global warming notwithstanding.



Factual errors

When Will and Summer are called to the hospital, a nurse tells them that Hampton has suffered an "aortal rupture." In medical terminology, all terms relating to the aorta are "aortic". There is no such word as aortal. Notwithstanding this, an aortic rupture is a life threatening condition. Anyone who has this would either be dead or in the Intensive Care Unit heavily sedated, not conversing easily like Hampton was. At the very least, he should have had a blood transfusion bag hanging over his bed.

When Will finds the copy of Jane Eyre April's dad gave her, the used bookstore owner says that the dedication includes "a quote from the book". In fact, the quote, though by Charlotte Bront?, is not from this book, but from her poem, "Evening Solace".

When Will is drunk on April's front porch after his birthday, he asks about Nirvana's song Come As Your Are. He quotes the song as "Come as you are, as a a friend, as known enemy." April corrects him by saying, "Memory, not enemy". In actuality, Will is correct because the lyric from the first verse is "Come as you are, as you were, as I want you to be. As a friend, as a friend, as an old enemy." April's lyric (actually "Memoria") appears in every verse thereafter.

In the beginning of the movie, on a close-up of the divorce papers, the word "Judgement" is used. In the USA, it should be spelled "Judgment".



Incorrectly regarded as goofs

Everything we see of the events that happened in the early 1990s (his first contacts with Emily, April, and Summer) is Will's recollection of how things happened. Since Will is retelling the tales of events that happened many years previously, how the events played out and any anachronisms (e.g. what people were wearing) is subject to the fallibilities of human memory.

During the scene where Will and April are smoking outside the store we see that Will's cigarette has a white filter. Will bought Morley Reds, which is a fictional brand used in movies. The pack has the appearance of Marlboro Reds, which have always had brown filters, leading some people to think his cigarette was a goof.



Miscellaneous

When Will runs up the stairs in the New Yorker Hotel we see he is staying on the 7th floor. Emily enters the lift bank on the right hand side of the lobby; those lifts go straight to the 20th floor and above. She could not have reached the 7th floor before him using those lifts.



Anachronisms

When Will first visits April in her apartment during the Bill Clinton 1992 New York primary campaign, April plays "In Spite Of Me" by Morphine (followed by Nirvana's "Come As You Are"). "In Spite Of Me" wasn't released until Morphine's September 1993 album Cure For Pain.

The cell phone number that Emily gives Will at Summer's party has a 212 area code. At that time, the 212 area code was for NYC land lines only.

When Will is talking to Hampton, the bookshelf behind Will has a hardcover copy of David McCullough's "Truman" on it, which wasn't published until June 1992.

In a scene just after the 15 minute mark, when Ryan Reynolds' character first arrives in New York in 1991, as he passes by the TGI Friday's on Eighth Avenue, a white Mercedes-Benz CLK convertible (W209 model) drives by, which could have been manufactured no earlier than 2003.

When Summer tries to sober up Will in 1991 (he's working on the first Bill Clinton campaign), she gives him a modern style bottled water - which was not available in 1991.



Crew or equipment visible

As Emily turns to walk away at the zoo, the transmitter for her wireless microphone is visible under the back of her sweater.

When Will starts calling people to reserve seats, the camera starts going around Will and for a few seconds, you can see a grip off to the far right (visible in wide-screen only).



Errors in geography

When Will is flying over Manhattan, he is arriving in the wrong direction. He is flying westbound and looking down the island of Manhattan. The major NY Metro airports are east and south of NYC.

The ends scene by April's apartment in Brooklyn shows a steam construction site with a stack in the background. In New York there is only steam in Manhattan, not in the streets of Brooklyn.



Character error

At the beginning of the movie, Will is narrating and says that his favorite days are Tuesdays and Fridays because he leaves work early to pick up his daughter Maya from school. (This particular day is a Friday, evidenced by the fact that Maya does not go to school the next day.) When Maya's mom is taking her home from the park the next day, Will says, "See you Wednesday," but he should have said "See you Tuesday," unless he and Maya's mom changed plans.