Jason Mewes (Jay) was so camera shy, that during the dance scene with him and Kevin Smith (Silent Bob), everyone had to leave and go into the video store, and just left the camera rolling, so that Mewes wouldn't be so nervous
The reason prices end in $.95, $.99, set under a round figure was so that cashiers would always have to open the register to give change, thus recording a sale and preventing them from pocketing the bills.
Jason Reitman has said that this film revealed to him his desire to be a filmmaker. Reitman later told Kevin Smith this, which lead Smith to jokingly quip, "You're the son of Ivan Reitman. You grew up on the sets of Ghostbusters (1984), and Stripes (1981). It took ME to let you know that you can be a director?".
Kevin Smith worked in the store where they shot the film. They shot for 21 straight nights. He would clock on at 6am and finish at 11pm. They would then shoot till 4am, after which he would try to grab an hour or two's sleep before getting ready to go back to work.
The film's shoestring budget is part of the reason it was shot in black and white. A number of different types of lighting were used, and this would have required a lot of post production to resolve issues related to the varying color temperatures. With black and white, this isn't a problem.
Filmed at the same store in which director Kevin Smith was working at the time. As he was only allowed to film outside of business hours, and because bright enough lights couldn't be afforded, the plot included an explanation for the shutters being always down.
The "Clerks" logo is made out of letters cut from various magazines and food items. The C is from Cosmopolitan Magazine, the L is from Life, the E is from Rolling Stone, the R is from Ruffles potato chips, the K is from Clark Bar and the S is from a Goobers box.
The scene where Dante confronts Caitlin about her marriage to an Asian design major in the video store is done in one shot, which lasts for over five minutes. It was shot on the first night of filming.
Kevin Smith has said on speaking tours that the reason he cast himself in the movie was that if the movie failed and he was in near-permanent debt for the rest of his life, he could at least point at his face in the movie as proof he did it.
Randall and the Happy Scrappy Hero Pup lady are not actually in the room at the same time. Jeff Anderson refused to read the list of porno movies in front of her, and particularly in front of the child (although the reaction shots of the Happy Scrappy Hero Pup lady were obtained by reading the list to her).
Despite having almost no violence in the film (with the exception of the fight between Dante and Randal), it was originally given an NC-17 rating by the MPAA based solely on its graphic dialogue. The film's distributor Miramax hired attorney Alan M. Dershowitz (of the O.J. Simpson defense team) who successfully petitioned the MPAA to lower its rating to R without any cuts.
According to Kevin Smith in an interview in the book "My First Movie", part of the movie's financing came from an insurance settlement. The settlement was from a car that he and Jason Mewes both drove, that was destroyed in a flood. Jason Mewes had told him there would be a flood, and asked if he could move the car uphill, but Smith didn't trust him.
The anti-smoking sentiment in the film represented Kevin Smith's own viewpoint when he wrote the screenplay. Silent Bob doesn't inhale when he puffs on his cigarette because of this. After filming this movie, he became a two-pack-a-day smoker.
According to an unfilmed scene that was animated and put into the 10th anniversary DVD, Clerks. (1994) takes place on Saturday. In Mallrats (1995), a reference is made to Julie Dwyer dying "yesterday". Mallrats takes place on Friday.
Willem Black was supposed to be a collegiate type, but the original actor for the role, Dan Hapstak, changed his mind and opted out of the role. Scott Mosier was then cast as the role, but since he didn't look collegiate, they reworked the character into an idiot man child.
There are at least two different versions of the scene where Randall is ordering a video for the woman with her little girl. The two versions have two distinctly different voices for the little girl when she says "Happy Scrappy"
Of the 50 actors credited, only two had at least one film credit before appearing in this movie (Gary Stern and Mitch Cohen). The other 48 made their first on screen appearance in this movie, most of them would become regular faces in many 'Kevin Smith' (I) films while others would only make this film.
While Randal (Jeff Anderson) was telling Dante about his cousin Walter breaking his neck attempting auto fellatio, when Dante asked if Walter made it and Randal said yeah, Anderson almost forgot the next line ("Balls resting on [Walter's] lips"). They decided not to redo the scene to make it so Randal was sympathetic about his cousin's death.
Kevin Smith and Scott Mosier attended the Vancouver Film School, British Columbia, Canada and made a pact that whichever of them first started directing a movie, the other would produce. Smith created his film first, and Mosier produced it, as he has all of Smith's films.
Dante wears a Pittsburgh Penguins jersey during the hockey game, playing against opponents wearing New Jersey Devils jerseys. Randal wears a USSR (CCCP) jersey during the game, but wears a New Jersey Devils hat.
Vincent Pereira originally had a scene in which Randal (Jeff Anderson) talks to a clerk at Big Choice Video, a perfect clerk, but the sound machine gave way in the middle of the take and they had to scrap the scene. Sound survives up until that point.
After the fiasco involving Caitlin and the dead guy in the bathroom, Randal is pulling a chip through a jar of salsa saying "we're gonna need a bigger boat..." alluding to Jaws (1975), one of Smith's favorite movies.
There are multiple conversations and references to the films including, but not limited to, Randall's discussion about the end of Return of the Jedi and the song about Chewbacca.
The trivia item below may give away important plot points.
One of the early scripts penned by Kevin Smith involved Dante being shot in the chest by a robber at the end of the film, after Randal leaves the store. This scene, devised simply because Smith didn't know how to end the movie, was actually filmed but was cut from the released version. It was later included on the 10th Anniversary DVD.