Only one work of fiction was produced for the toyline: a booklet/picture book titled "Wave Dancer is Missing!", unsurprisingly featuring Wave Dancer as the lead. Otherwise, any and all characterization comes from the back-of-the-box descriptions. There were also two partially animated commercials that helped the world-building along.
The My Pretty Mermaids franchise provides examples of:
- Amazing Technicolor Wildlife: All of the pretty mermaids come in bright, bold, and, above all, many colors. The brightest are the Sunsparkle Mermaids.
- Bioluminescence Is Cool: Evoked with the Moonglow Mermaids, who have glow-in-the-dark tails.
- Chest Insignia: Each Pretty Mermaid has a unique so-called name design on her fin, much like earlier each Little Pony has a unique hip insignia and each Fairy Tail has a unique chest insignia. But unlike the other two, a Pretty Mermaid's name design only becomes visible if the fin is dipped in cold water, or in case of the Moonglow Mermaids, if the light is turned off.
- Duet Bonding: When Wave Dancer is captured by fishermen to be sold in "Wave Dancer is Missing!", a human boy happens to pass by her cage at night. He cannot understand her pleas to be set free, but does settle down next to her and plays the flute. Wave Dancer dances to the tune, which convinces the boy to set her free.
- Everything's Better with Rainbows: Rainbows are very often referred to in the My Pretty Mermaids line. It's at the end of which the pretty mermaids live and it's the rainbow that gives them whatever they desire, be it furniture or babies. There's also the Rainbow Mermaids, who have triple-banded tails.
- Everything's Better with Sparkles: Both the Moonglow Mermaids and the Gembright Mermaids have glitter fins. Somewhat curiously, the Sunsparkle Mermaids have nothing sparkly about them. The name refers to them being in neon colors.
- Expy: Of the Little Ponies, of course! The fact it's the mermaid named Sea Pony that is in the opening scene of each commercial might be meant as a Shout-Out.
- Flat Character: With, for the most part, only the back-of-the-box descriptions for characterization, it depends on the exact description whether the trope is in effect or not.
- Improbably Female Cast: There's only two male toys released in the lineup, whom are both part of the Seaside Wedding playset. One's the groom and the other is the newborn boy, but it's 50% chance he's included in the set instead of the newborn girl.
- Our Mermaids Are Different: The pretty mermaids are your regular kind-hearted human-like seafolk. They're just a lot more colorful than average and have those name designs on their tails.
- Race Lift: The first quartet of mermaids came in light skin and dark skin. Same characters, but different races. Hasbro called it a day at that, producing all following quartets in light skin only and only featuring the light skin versions of the first four in artwork.
- Recycled Sound Track: The commercial tune for My Pretty Mermaids is exactly the same melody as the My Little Pony tune.
- Recurring Element: Between My Little Pony, Fairy Tails, and My Pretty Mermaids, it's rainbows and insignias.
- Seashell Bra: Not quite, but close enough. The mermaids wear normal fabric bras that have a decorative shell in the center. The exception are the Gembright Mermaids, who have Gem-Encrusted bras.
- Separated at Birth: Sort of. The packaging of the Seaside Wedding playset shows two newborns, a boy and a girl, within the seashell. However, only one of the two is actually available in the set (and which one that is is random).
- Sugar Bowl: As the lyrics go: "I believe the prettiest rainbow leads to a magical sea."
- Toyless Toyline Character: In "Wave Dancer is Missing!", MerMadame, Dolph the Dolphin, and an unnamed human boy are all story-exclusive characters without toy counterparts. There's also a bunch of fishermen, but they only serve to cause the problem that needs to be overcome.
- Vague Age: All of the dolls have the same mold and thus should be about the same age. However, while two mermaids get married and have a baby in the Seaside Wedding playset, the booklet "Wave Dancer is Missing!" has the mermaids attending a school run by a story-exclusive mermaid that's drawn to be considerably more adult-looking.