Armor-Piercing Response: When Sweet Pea criticizes Weatherbee's decision to expel the Southside students from Riverdale High, saying he blames them for ruining the school, Jughead quips, "to be fair, you did," since Sweet Pea did destroy some property without reason.
Back for the Dead: Tall Boy is revealed to have been acting as a decoy Black Hood, and to have died. After being completely absent since Chapter 25, no less.
Bait-and-Switch: The episode opens with Archie, Veronica and Betty at Jughead's grave, only for it to be revealed that he's alive and snapping out of his coma.
Bookends: Of a sort. This isnt the first time the season finale included someone getting their Serpent jacket-except this time, its Cheryl, of all people.
Chekhov's Gunman: Cassidy, who Andre killed back in "The Hills Have Eyes," turns out to have been far more than just a throwaway character, as Archie gets arrested for his murder at the end of the episode.
Cliffhanger: As with last season, the finale ends on a huge one.
Custom Uniform: Cheryl joins the Serpents, but of course she gets a lovely, atypical crimson jacket.
First Kiss: Kevin and Moose. Notable because they have been in a state of Ship Tease for two seasons (and it is not clear that this is the end of that) as well as Moose's own insistence in Chapter One that he was willing to do anything with Kevin except kiss.
He Didn't Make It: Subverted; Fangs turns out to be alive, despite last episode having FP declare him dead.
It's All My Fault: Betty blames herself for the people her dad murdered for not figuring out he was the Black Hood sooner.
Offscreen Moment of Awesome: The fight between the Ghoulies and the Serpents, as well as Tall Boy's shootout with the police. Neither of these events are shown, and are only recounted to other characters after the fact.
Pet the Dog: Penelope of all people has this when she warns Cheryl that Hiram plans to raid the Whyte Wyrm.
Real Life Writes the Plot: Word of God reveals there was originally more plotlines planned out for Tall Boy. However, all those plans had to be scrapped when the actor portraying him got a serious neck injury. Possibly explains why Tall Boy was not seen since 2.12 and was hastily killed off-screen with a throwaway line.
Archie leaves the hillbilly who attacked the core four at the Lodge cabin in Andre's hands way back in 2.14, and hears a gunshot as he walks away, clearly indicating Cassidy was killed. For a while, there seemed to be no consequences or repercussions to that murder, until this episode when Archie is arrested in front of the whole school for Cassidy's murder.
Hiram's reactions to Veronica and Archie: He cuts off Veronica's inheritance when she buys Pop's from him and he frames Archie for murder when Archie threatens him. Basically, don't go around threatening and messing with a mob boss.
Hermione ends up victorious against Fred because she and Hiram bought votes and played on the town's hatred of the South Side.