Continuity mistake: When Sandy meets Rebbecca in the coffee shop to discuss her running away, Rebecca's coffee cup alternates from being down on the table to by her mouth, when you see her from behind, between shots.
Factual error: How exactly does Seth unlock the door? The entire purpose of locking the storeroom is to keep mall customers out so they won't steal things, not to keep people in there, so there is no way it was only lockable from the outside. If it was a key operated lock, why would someone just leave their key in the keyhole for someone to take? There is no explanation for Seth being able to unlock the door.
Continuity mistake: In season 2 episode "The Risky Business", the top Summer holds changes position in her hands.
The Return of the Nana - S2-E21
Continuity mistake: Marissa's arms change position repeatedly while she and Trey are down at the beach. Also, her bag appears with her, even though she left the apartment without it.
Deliberate mistake: Lindsay is not at Caleb's funeral in the last episode of season 2, "The Dearly Beloved". It's unlikely that she would have missed it - she is still on good terms with him and he is her father, the only reason she left was to be with her mother, not because she didn't love Caleb.Obviously they didn't want to create another drama with having Lindsay there while they had to focus on the important story-lines - Caleb's death, Kirsten's drinking and Marissa shooting Trey.
Continuity mistake: At the beginning of the first episode of Season 3, "The Aftermath", Ryan's hair is much shorter than it was at the last episode of season 2. Since they arrive at the hospital with a bleeding Trey, we know that this is right after Trey got shot. It doesnt make any sense that Ryan would go get a haircut right after Trey got shot and then go to the hospital with him.
The Shape of Things to Come - S3-E2
Continuity mistake: At the beginning of the second episode of season 3, "The Shape of Things to Come," Summer, Marissa, Ryan and Seth are ordering pancakes at the restaurant. In this whole scene, Marissa's blue mug keeps changing position between shots.
Continuity mistake: Season 4 Episode 5 The Sleeping Beauty: When Taylor calls Ryan in the middle of the night (around 03:03 when he first checks), the second time Ryan checks the time on his radio it shows 03:23, however it jumps back to 03:04 when he looks again.
The Earth Girls Are Easy - S4-E8
Continuity mistake: Season 4 - Episode 8 - The Earth Girls Are Easy - When Kaitlin is at the party, talking to Bullit, her strand of hair changes from hanging over her eye to hanging down next to it, without her moving her hands or head to displace it.
The Case of the Franks - S4-E13
Revealing mistake: When the limo pulls up to the hot dog stand, Julie steps out from the back seat. And as she walks toward Frank standing in front of the picnic tables, the limo driver is visible behind the wheel. Julie joins Frank at a table, and then Ryan decides to enjoy a last spin in the limo telling Taylor they've rented it for 2 more hours. In the next shot they are sitting in the front seat talking while Ryan is at the wheel, when the limo driver never left the vehicle. (00:41:20 - 00:42:46)
Answer: He means that if Alex has to go so far as to forbid Ryan from seeing Marissa in order to maintain her relationship with her, their relationship obviously isn't working.