H₂O: Just Add Water/YMMV

Nightmare Fuel:
- The girls' Superpower Meltdown.
- The mutation Emma went through in that Season 2 episode after cutting her finger on a piece of coral.
- And also that water tentacle that attacks the girls in Season 3.
Fridge Logic: So how do they avoid being seen in the school loo? Do they just not go in public?
- I'm not sure why that would be problematic for them. People don't normally get splashed with liquid when going to the bathroom, if they're doing it right.
  - Yeah, but do they just use Purell or what?
  - Brought up in-series when Kim notices she's never seen Cleo washing her hands.
  - They have ten seconds to dry off before the change kicks in. That's enough time if you're quick, have paper towels handy, and maybe wash them twice.
Germans Love David Hasselhoff: It's a hit in The UK, Central and Eastern Europe, to the point that the 3rd season aired in the UK first before Australia got it... by a year.
Moral Event Horizon: Charlotte crossed it when she in the second-to-last episode stole Cleo's lockett and made her believe that Lewis no longer cared about her.
Retroactive Recognition: Emma's Season 2 Love Interest, Ash, became the True Seeker.
The Scrappy: Good God, Kim. Many, many of the show's fans have expressed the deepest desire to punt her through a window for her constant attitude.
Toy Ship: One episode had Emma's younger brother Elliot trying to ask Cleo's younger sister Kim out. Kim just took advantage of him and kept bossing him around. He eventually got tired of her attitude and ditched her at the end of the episode.