Bonding Over Shared Trauma: While in Dolores' room, Isabella admits that while being the village pariah is pretty bad, she'd have taken it any day over being the pride of the village. Hiccup comes to the conclusion that they've both suffered at the hands of family members.
The Dog Was the Mastermind: The whole chapter was orchestrated by Mirabel as a "bonding exercise" for Isabela and Hiccup.
Empathic Environment: After Casita's reconstruction, Isabela's room had become this. While it was originally wall-to-floor flowers, the environment now shifts and changes depending on her mood, usually to accommodate her growing fondness for cactuses and succulents.
Sometimes a dry, arid desert, littered with cacti. Sometimes a murky bog, filled with lily pads and water sausages. Or an expansive field, populated by tall sunflowers swaying in the breeze. But no matter what, her living space always stood in the center. A greenhouse, with her bed and other personal accommodations being placed inside. It was colorful, versatile, and ever-changing.
Fool's Map: The Treasure Map wasn't created by Casita, but by Mirabel as a protracted trust-exercise for her sister and boyfriend.
It's the Journey That Counts: Enforced, since the whole point of the quest was to get Isabela and Hiccup to like each other.
Hiccup: So... the real treasure was the friendship we made along the way? Isabela: That's the stupidest thing I've ever heard...
Never Smile at a Crocodile: While looking for a clue in Antonio's room, they come across a crocodile. Apparently it's close enough to a dragon that Hiccup could tame it.
Isabela: Do you just have a thing with lizards? Hiccup: That's a distinct possibility.
The Gate Guardian trial Camilo gives to Isabela and Hiccup mirrors the Bridge-Guardian scene from Monty Python and the Holy Grail. Even the "questions three" he gives are the same, both Isabela and Hiccup passing the trial after admitting their favorite colors.
Hiccup: Uh... green. Isabela: Anything but pink.
Vitriolic Best Friends: Hiccup and Isabela evolve into this by the end of the chapter; still willing to throw shade at each other, but have moved past "barely tolerating each other for Mirabel's sake."
Mirabel: Nothing brings people together like a perilous expedition!
