In Equestria, the sirens' true appearance is a Hippocampus. Upon releasing their full powers in the human world, the Dazzlings are shown to possess translucent fin-like wings in their anthro forms, unlike their true forms. Their siren forms are summoned as astral projections from their pendants and used to weaken the Rainbooms.

Arriving at Canterlot High, Aria takes the appearance of a slender teenager with pale-mauve skin, purple eyes with purple-mauve eyeshadow, and long, violet hair with aqua-green streaks, kept into pigtails by large, silver star-like holders. She dresses in a dark purple-trimmed white sleeveless top under an aqua-green jacket with most of the sleeves being ripped off, magenta-purple skinny jeans with sparkly-patches on the sides, and calf-high, plum-purple high-heeled boots with both lighter-colored straps and darker-colored soles and heels. She accessorizes with three, dark purple arm bands on her wrists, a similarly-colored multi-strapped belt with a silver star hung from her waist, and a black choker with a ruby pendant around her neck.

In Sunset's Backstage Pass, she now has a small purple neckerchief around her neck, and wears a short-sleeved lime green fluffy jacket over a magenta long-sleeved shirt with white polka dots, even darker purple pants with aqua-green accents on the back and bottom pant legs, and purple boots with lime green fluffs on the back.

Arriving at Canterlot High, Sonata takes the appearance of a slender teenager with pale sky-blue skin, magenta-pink eyes with cyan upper-eyelids, and long, turquoise-blue hair with dark royal-blue streaks, kept into a high-ponytail with V-shaped bangs by a dark royal-blue hair tie. She dresses in a dark magenta vest with a brighter-colored popped-collar and cuffs, three pale sky-blue buttons with straps, and a light blue musical note surrounded by a brighter-magenta patch on the right side. She also wore a lavender-pink denim skirt, similarly-colored knee-high socks, and similar-length bright magenta high-tops with white soles and toes.

Sonata accessorizes with magenta bracelets with pale sky-blue spikes on both her wrists, and a black choker with a ruby pendant around her neck.

As a siren, Adagio has light brilliant gold skin with moderate gamboge eyes, moderate gold hooves and underbelly, and moderate amber fins, and has a red jewel in the center of her chest.

As a human, she is a tall teenage girl with yellow skin, magenta eyes, darker yellow eyeshadow, and orange puffy hair with yellow streaks in a ponytail with a violet spiked holder.

In the beginning of the movie, she wore a dull purple long-sleeved hoodie, grayish-blue jeans, and white sneakers.

Upon arriving at Canterlot High, she now wears a mauve violet mini bolero jacket with small shoulder puffs over a purple romper that stop slightly above the thighs and her cutie mark (an indigo music note with a gold gem) on the bottoms, a golden, spiky belt with a yellow gem around her waist, lavender tights with lilac triangle imprints, and dark purple below-the-knee boots with yellow gold-spiked bands around the ankles and gold-spikes on the brown medium heels.

In Sunset's Backstage Pass, she now has gold bands and black bracelets with gold spikes around her wrists, and wears a black leather jacket with gold spikes on the sleeves, a lavender sleeveless shirt with lilac triangle imprints and a black collar with gold studs, a gold neckline with a curved crescent-shaped brooch, a gold belt with a red and gold buckle, purple rolled-up shorts, and black and purple leather thigh-high, high-heeled boots with golden-orange studs on the top, black bands with her cutie mark on the bottom and gold spikes on the back.