When Jay and Silent Bob enter the convenience store, and Jay is talking to Dante about how Veronica is a good girlfriend, when he says "I know she does a lot for you.", his mouth doesn't move to the same phrase.
After the food fight, when Dante and Randal are sitting in the food and Randal is yelling at Dante while throwing candy bars at him, one of the candy bars does not make a sound when it hits Dante. Kevin Smith points this out in the 2004 commentary.
The Administer of Fines states that the little girl was sold cigarettes at 4 that afternoon. This is impossible because the sale occurred before the hockey game, which was at 2 p.m., and Dante and Randal were at the wake at 4 p.m. (Director admitted this in the DVD/LD commentary).
When Veronica chases the gum salesman and the customers, she says "Don't you have jobs to commute to?" She also is supposed to be in class all day. Later when Randal and Dante go to the wake, Randal says to Dante "It's 4 o'clock on a Saturday afternoon - how many people come to the store at four on a Saturday afternoon?" If it's a Saturday, how can there be classes all day, and why are the customers supposed to commute to their jobs? And we are told that the funeral is tomorrow which would be a Sunday. Funerals are not usually held on a Sunday.
The official who hands Dante the summons claims that the charge can not be contested in a court of law. The Constitution guarantees that any matter involving at least $20 is eligible to be ruled on by a jury of the defendant's peers. Director Kevin Smith briefly acknowledges this in the commentary.
Jay's costume is different in nearly every scene in the movie because the jacket he wore on the first day of shooting was his girlfriend's and he had a hard time borrowing it for the entire length of the shooting.
Dante's beard changes because Kevin Smith asked Brian O'Halloran to shave his goatee before filming started during rehearsals, then, after seeing what it looked like without it, told him to grow it back. The scenes shot earlier in the shoot show a thinner beard while the ones shot last show a thicker goatee as it had longer to grow back.
Veronica says she'll see Dante at closing after dropping off the lasagna. After she says this, Dante makes the call to find out that the boss is in Vermont and he will be stuck there until closing. When Veronica had spoken to him, he was still expecting to leave for his hockey game.
When Dante and Randall argue on the ground of the convenience store following their big fight, and all the food is on the ground, the "SKOR" bar placard on the shelf behind Dante disappears in one close-up shot.
Different "People" magazines in the rack in different shots. The first time, the cover story is about Soleil Moon Frye's breast reduction surgery. The second time, the cover story is about the death of Brandon Lee.
The amount of Dante's Yoohoo decreases rapidly between shots while discussing Star Wars: Episode VI - Return of the Jedi with Randall. The bottle is also turned to a different view of the label upon return shot.
While playing hockey and arguing with the irate customer Dante is using an Easton model hockey stick. When he takes a faceoff against that customer Dante is then using a Koho brand stick. After the customer loses the hockey ball Dante is then using the Easton stick again.
In the scene where a customer is complaining to Dante about Randal being late, there are 7 videotapes (6 on the counter and one in the customers hand). A few minutes later when Randal arrives, Dante hands him only 3 tapes to return to the video store.
In the second shot of William The Idiot Boy (after Dante and Veronica stand up from behind the counter and sees William staring into space), the leg of a man can be seen moving quickly to the left-hand side of the screen - it's the clapperboard man, who didn't clear shot fast enough.
At the end of Caitlin's confrontation with Randall, Jeff Anderson momentarily breaks character and admires Lisa Spoonhauer's butt as she walks away. (Kevin Smith points this out in the DVD/LD commentary.) However, due to Randal's sexual obessions, this action was completely in character for him.
Throughout the movie by the quick stop counter we see 3 different sets of TV guide covers. One with Heather Locklear one with Tim Allen from home improvement and one with Ted Danson. The movie is suppose to take place in one day and yet we see these TV guides and spread out out of sequence.