Jamie (Michael Cera), a young American traveling in Chile, is eager to experiment with mescaline. He plans to journey out of town with his friends, the brothers Champa, Lel, and Pilo (Juan Andrés, José Miguel, and Agustín Silva), to look for the San Pedro cactus, boil it into juice, and drink it on a beach. The night before they plan to leave, Jamie "accidentally" invites a fellow American, a young woman calling herself Crystal Fairy (Gaby Hoffmann).
Crystal Fairy & the Magical Cactus contains examples of:
- Affectionate Nickname: Crystal refers to Jamie as El Pollo Loco, which gets shortened to Pollo. By the end of the movie, the brothers have picked it up too. Less affectionately, the guys call her Crystal Hairy.
- Animated Credits Opening: A black-and-white animation involving constellations, a fairy turning cacti into crystals, and various elements from the movie.
- Bilingual Dialogue: Much of the dialogue is in a mixture of English and Spanish.
- Campfire Character Exploration: Their first night on the beach, the characters describe what they're scared of. The second night, they each tell a secret.
- Given Name Reveal: Crystal introduces herself to a man who gives her a lift as Isabel.
- Granola Girl: Crystal is a New Ager who complains about sugary cereals, attempts energy rituals, and puts "magic pebbles" in the guys' drinks so they can consume the essence.
- Hurt Foot Hop: Crystal tries to climb a cliff, steps on a sharp ledge, and hops up and down. The next time she tries, she wears sneakers.
- Jump Scare: A shot of a wizard doll is suddenly interrupted by a short shot of a screaming face.
- Lens Flare: Visible in some of the outdoor scenes.
- Nobody Poops: Averted - an early scene has a prostitute awkwardly peeing into a bush while her friend tries to cover her.
- No Periods, Period: Averted - the guys talk about how they'll have to pick up tampons now that Crystal's with them.
- Potty Emergency: While the group is driving through the desert, Crystal insists on stopping because she has to pee.
- Rape as Backstory: When Crystal was seventeen, she took a mysterious drug at a party. The next thing she knew, five boys were raping her in a boathouse.
- Screw the Money, I Have Rules!: Crystal speculates that this is the reason why it's so hard to find anyone willing to sell them San Pedro cactus, even though lots of yards have it.
- Shameless Fanservice Girl: Crystal leaves the shower naked and doesn't get dressed until the guys tell her she's making them uncomfortable.
- Vapor Wear: Crystal never wears a bra.