In the scene where Charlie takes Daisy back to his parents' summer home for the first time, her hair goes from curly when they are outside to flat-ironed when they are indoors.
In the opening restaurant scene, the pitcher Daisy gives to the three men at the table changes from half full when she picks it up to nearly full when she sets it down on the table.
After Kat gives the food critic the bill and picks up his pizza, you can see that the pizza is still whole, even though he has taken a slice and eaten part of it.
It was incorrectly regarded as a goof that after Charlie and Daisy's first date, Daisy is wearing a strapless black dress with a white bow on their date, but when entering the house after the date she has a long sleeve black dress on. The black dress is worn on a subsequent date, The previous scene shows that the girls worked a shift at the restaurant between the dates.
Several times throughout the movie, Kat's sideburns change from short to long.
You cannot enter Yale University as a freshman in February, at least in 1988.
Incorrectly regarded as a goof, the business license next to the phone at Mystic Pizza reads that the establishment as being in Groton CT. Mystic is a village within the town limits of Groton.
At the beginning of the film, the altar boy mouthed the priest's lines.
When Jo picks up Kat from the babysitter's house, Kat's door to the delivery vehicle never latches. When Jo hits the accelerator, you can see the door fly open while Kat is seated. In the next scene while driving on the road the door is secured.
The alleged Portuguese surnames that are given to the characters are actually wrongly misspelled and mistaken with Spanish. "Arujo" should be Araújo and "Barboza" should be Barbosa.
During the bar pool scene, Charlie doesn't make the solid orange ball, but when Daisy runs the table and eventually wins the game she doesn't sink the orange ball either.
In the scene where Kat has brought her mom pizza down at the docks Mrs. Araujo asks, "Hey, Sylvio, you got a job for my smart kid?" Sylvio shakes a dead octopus at her and replies something along the lines of, "Yeah, right here" but is smiling broadly the whole time and does not move his lips.
When Bill is sitting in the bar and Charlie first walks in, the audio of him talking about Charlie does not match up with what it shows him saying.
When Charlie offers Daisy a beer while having dinner at his parent's house, she says, "No, thank you," but her mouth isn't actually moving.
When Tim and Kat touch their glasses together in a toast, the glasses make a distinct ringing sound. However, they both are holding their glasses by the bowl, which would result in a clink rather than a ring.
When Jo, Kat and Daisy take Bill's truck for a joy ride; as they belt out Aretha Franklin's "R-E-S-P-E-C-T," an earpiece is clearly visible in Jo's left ear. The device is not present in other scenes.
When Kat returns home wearing Tim's sweater - as she's exchanging dialogue with Daisy you can see a crew member leaning low while holding a boom mic cable in the mirror.
When Kat begins to stand up after meeting Phoebe for the first time the power pack from her wireless microphone can be seen bulging in the back of her sweater.
When Jojo is arguing with her boyfriend as his fishing boat is heading out to sea, the boat is actually going up river. This is hidden pretty well, but Mystic residents have noticed.