In an early scene, Rob Schneider attempts a golf drive by running up to the tee before swinging. Adam Sandler says, "That's the stupidest looking swing I've ever seen." This is a joke on Sandler's character's trademark golf swing in Happy Gilmore (1996).

Lucy is treated at the "Callahan Institute", which Dr. Keats (Dan Aykroyd) tells Lucy's family is funded by an automotive magnate, T.B. Callahan, out of Sandusky, Ohio. In Tommy Boy (1995), Chris Farley plays Thomas Callahan III, who runs an auto parts factory in Sandusky that's being threatened with foreclosure by Dan Aykroyd's character. Tommy Boy (1995) was also directed by Peter Segal.

The original script set the movie in Seattle, the hometown of scriptwriter George Wing.

Rob Schneider's character Ula was inspired by Siope Samuela Ula Lomu, a Tongan concierge at a luxury rental property at which Schneider, Adam Sandler and Drew Barrymore are regular visitors. Lomu has the same blinded, grayed-over left eye that Schneider's Ula has, but there's not much resemblance beyond that. Says Lomu, "They aren't like some other top Hollywood people. They're really normal."

"Jocko" was played by Sivuqaq, one of four walruses living at Six Flags Marine World in Vallejo, CA. The three female walruses featured in the film are named Siku, Uquq and Qiluk.

When Henry and Lucy are first at his place they see two dolphins that Henry calls Mary-Kate and Ashley after the Olsen twins.

The book Lucy reads at breakfast, "Still Life With Woodpecker - A Sort Of A Love Story" by Tom Robbins, is a love story set in Hawaii.

The neurological condition that Lucy suffers from, Goldfield Syndrome, is entirely fictional. True anterograde amnesia affects either short-term memory, which can last minutes or seconds, or intermediate-term memory, which can last days or weeks. Falling asleep has nothing to do with the condition, and sleep actually intensifies many chemical effects which help memory.

In an early scene a dentist and a woman in the dentist's chair are seen talking with each other. The woman playing the dentist is Jackie Sandler, Adam Sandler's wife. And the woman in the chair is played by Linda Segal, director Peter Segal's wife, who actually is a dentist in real life.

Originally entitled "50 First Kisses".

Henry makes a video for Lucy to remind her of the events that have occurred since her accident. One of the items is "Red Sox win the World Series..." followed by "... Just Kidding". During the year of the film's release, the Red Sox actually broke an 86-year drought and won the World Series. Drew Barrymore made the movie Fever Pitch (2005) about an avid Red Sox fan and they filmed the final scene on the Busch Stadium field while the Red Sox celebrated winning the 2004 World Series.

This movie reveals the ending of The Sixth Sense (1999)

Actor/Producer Anthony Begonia was set to play a cameo as an ukulele player but was unavailable.

In the first scene where Henry walks into the Hukilau Cafe', Nick can be seen wearing a gray greasy tank top with the "W Y" logo of the Weyland-Yutani company from the Alien movies.

The Cafe that they keep meeting at is actually a house they fixed up for the movie. It is located on a macademia nut farm on the eastern side of Oahu. The same house was used in Tears of the Sun (2003). And they also filmed scenes from Jurassic Park (1993) in the open fields nearby.

In the ending credits, a remake of the song "True" is sung by Will i Am and Stacy Ferguson. This same song is sung by Steve Buscemi at the end of The Wedding Singer (1998).

Continuity

Near the end when the patient asks Lucy what he's doing, she tells him he's painting a picture, and he is seen holding a paint brush. When the picture he "painted" is then seen, it actually is done in crayon.

When Ula is beating up Henry, Lucy is taking off her sunglasses and pulls off to the left-hand side of the road. In the next shot, Lucy is farther away and driving up in the middle of the road.

At one point in the diner when the waitress takes a guy's order, he says he'll have the pancakes and she takes the menu away from him. In the next shot, he is in the background and still holding the menu open.

When Alexa and Doug are waving goodbye to Henry at the boat dock, Alexa is wearing her watch on her right wrist; a moment later as she grabs Doug's behind the watch is on her left wrist.

After Henry has stitched up Ula's side, it is very red. However, when Ula and Henry are in Henry's that same night or the next, Ula's shark bite looks mostly healed, almost like a scar, without any visible stitches.



Factual errors

There are no walruses at Sea Life Park in Hawaii.

The beach where they have their first, first kiss faces south. The moon is lit from the left which is east. That would mean the sun is coming up in the evening.

After Lucy gets issued a ticket, she grabs a customer's copy of the Honolulu Star Bulletin to confirm the date, then runs to the newspaper stand to reconfirm it, but she's able to open it without putting in any coins. The Honolulu Star Bulletin, eased publications on June 6, 2010, was not a free newspaper. It's remotely possible the lock is broken, and as a regular of this caf?, she knows about it.



Incorrectly regarded as goofs

When Henry goes to visit Lucy at the Institute, she says, "I don't know who you are, but I dream about you almost every night." Since she has no memories of anything after the accident, it seems that she could not possibly know that she had dreamed about Henry more than once, but she very likely made note of it in her journal. Also, since she appears inclined to paint her dreams many (all?) nights, the mere collection of paintings tells her this is a frequent occurrence.

The last time Henry plans to trick Lucy by tying himself up in his pickup, Marlin and brother Doug appear instead. Marlin tells Henry to come to their house after he is done playing hostage with Lucy. When he does, Lucy is singing The Beach Boys songs. Marlin tells Henry she only does that on the days she's met Henry. This presumes that time has passed and Henry had seen her that day.

After showing Henry her diary, Lucy tells him "sometimes when I watch it [the video tape] I feel like I'm being told about my life..." It could seem like, because she loses her memory every night, she wouldn't know how she 'sometimes' feels about watching the tape. However, as has just been revealed, she writes this journal herself to herself. Most likely the first entry was identifying this as the reason for her journal, and since it seems likely she's been getting the video before the journal (seeing as nobody knew about this journal until now), she probably has legitimately had this feeling many times and took note of it each time.



Revealing mistakes

When 10 second tom is first introduced he shakes everyone's hands and then does so again after ten seconds, not remembering them. Yet he knows where he is and recognizes the doctor without having to be told again.

During a montage sequence, Doug is doing sit-ups from a hanging object attached the ceiling, and it breaks off, causing him to fall to the ground. Rather than having Sean Astin in the closeup, his stunt double is used instead.

When Ula is on the boat when Henry is repairing it, he has only the slightest white scar. It is only three days after he got bitten and it is only a pale, nearly invisible scar. When he falls through the boards and says his stitches reopened, that is nearly impossible seeing as how it was only a scar and there was no stitches.



Miscellaneous

When her father is watching the Vikings game it is implied that its evening, but due to the time difference with the mainland the game would be on at 7am or 2pm at the absolute latest, and therefore not at night in Hawaii.



Audio/visual unsynchronized

An Epson Stylus inkjet printer is seen, but the sound of a dot-matrix printer is heard.

The type of penguin used for the film was an African Penguin. The sound effect used is not the actual vocalization that bird. The actual call they make sounds like a donkey braying.



Errors in geography

The scene where Henry is playing golf there is a large island in the background. On O'ahu, none of the other Hawaiian islands are visible.



Character error

A police officer tickets Lucy for having expired license plates while her truck is legally parked in the parking lot of the pancake house. Since the parking lot is on private property, and Lucy is not driving the truck when the police officer tickets the expired license plate, he does not have a legal right to write her a ticket. (In some cities police can cite cars on private parking lots.)