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 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.
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.
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.