Continuity mistake: During the pep rally it is raining hard and everyone on the football field is soaking wet, but when Cheryl runs from the field into the locker room followed by Veronica and Betty, they are all completely dry and their hair is perfectly styled.
Other mistake: Archie's uncle Frank tells Archie during an argument with him that he is 40 years old, with seven years in combat while in the military. But in a previous episode when explaining why he let Fred take the blame for his DUI, he claimed that he was a Desert Storm veteran in between tours at the time. Either the show got the wars wrong and meant to say he was an Operation Enduring Freedom or Iraqi Freedom veteran (no actual veteran uses "Desert Storm" when referring to combat in the Middle East after 9/11) or they're saying that he was only 10-11 years old when he went to Desert Storm. (00:29:30)
Continuity mistake: In Season 4, Archie visits his father's grave. On the grave it says May 21, 1970 - July 3, 2019, but in season 5, Veronica says "It's 2021" Veronica says this seven years after Archie visits the grave, so how has it been 7 years from 2019 to 2021?
Factual error: Archie revealed to his friends that he joined the Army to avoid repeating his senior year and was shipping to Basic Combat Training the following morning. Before he could leave, he would have to wait for his background check and waiver for his juvenile record to be processed (dropped felony charges still require a waiver in the Army), which could take several weeks. Also, he would need to already have his diploma or a GED to ship to Basic; the Army stopped accepting dropouts several years ago.
Continuity mistake: As someone knocks on the door, Betty drops her bowl of cereal leaving a mess consisting of milk, "Fruity Munch" cereal, and shattered ceramic on the floor. When Betty walks forward to open the door, the floor behind her, where there should be a huge mess, is totally clean. (00:08:01 - 00:08:27)
Continuity mistake: When Betty and Jughead are fighting in front of Archie and Veronica, Jughead is holding his drink when the argument first starts. When the camera switches to show Archie and Veronica's reactions, the drink is sitting on the table.