Alice and Charlie have a massive dispute that creates irreconcilable differences between them, while on a literal sinking ship. That Bob owned. And Alice is responsible for it sinking. Which Bob won't forgive her for.
Alice is Bob. And so is Charlie. Cue subtitles saying "Problem, Shippers?"
Charlie pulls a Face-Heel Turn and turns into a villain openly antagonizing Alice and Bob and quickly crossing the Moral Event Horizon, part of what caused the turn being some bad moments in Alice and Charlie's past together.
Justified: They had always intended for Alice and Bob to get together, but over the course of the episodes they realized they'd created a Relationship Writing Fumble for Alice/Charlie and needed to correct it.
Double Subverted: Turns out they aren't brother and sister at all, but discover Alice's mother killed Charlie's father, and neither can stand to be around the other any longer.
Parodied: They spend an entire episode sinking every ship on the show, even completely non plausible ones.
Zig Zagged: The ship keeps getting sunk and refloated every so often, completely infuriating both the Alice/Charlie shippers and the Alice/Bob shippers. Or it's part of the Star Wars extended universe, and you've got writers fighting over the ship using actual canon.
Invoked: Charlie forces Alice to confess or explain her feelings, and those feelings are platonic.
Defied: Charlie refuses to give up on Alice.
Discussed: "Look, Alice, I think Charlie might have some feelings for you. You should think about telling him you're not interested."
Conversed: "There goes Charlie and Alice. Poor guy. Sucks to be in love with someone not interested."
Deconstructed: Alice ends up alone and miserable, wishing she'd taken the chance to be with Charlie.
Played For Laughs: Bob acts as a Shipper on Deck for Alice/Charlie, and all her attempts to get the pair together end up highlighting all the reasons why the relationship doesn't work, and why Alice/Bob would.
Played For Drama: Charlie has had a crush on Alice for a while now, whilst Alice has been content not to hurt their friendship. Charlie overhears a conversation that leads him to believe that Alice might like him finally, he makes a move for her... and is brutally shot down, as well as finding out that Alice loves Bob instead. This leads to severe jealously and anger for Charlie towards Bob. It also threatens the foundation of the Alice/Charlie friendship, perhaps to a point where Charlie thinks about leaving.