Mylène is short and chubby with golden brown eyes and blonde hair, with some strands dyed green, blue, and magenta, put in dreadlocks. One dreadlock on her left side of her head has a purple cat bead, and another dreadlock on her left side has a golden loop.
She wears a pink bandanna to hold her hair back, and she has a necklace with a stone pendant. She wears a periwinkle shirt with a white silhouette design on the front of a bird holding a branch with leaves, which is underneath an olive green hoodie jacket. There are pins attached to her jacket: on the right side, she has a daisy pin; on the left side, she has a ladybug pin, a panda pin, and a yellow and green pin. Additionally, she wears dark gray jean shorts, black leggings, and dark purple and white sneakers.
Polymouse wears a medium gray, pink, and light gray mouse themed superhero jumpsuit with a faded-pink color from her hips to her neck, and is grey from her torso down to her ankles, divided by her Jump Rope. As well as a medium gray jacket with a hood which bears mouse ears. Behind her medium gray mask (but little lighter), her eyes are moderate green. And her hair becomes forehead length with pink dreads.
Horrificator is a large salamander-like monster with long brilliant purple tail, the top half of her body mainly brilliant fuchsia and the bottom half, along with her forearms, are the same color as her tail. She has three brilliant amaranth eyes with light brilliant gold sclerae, the third eye being in the middle of her forehead, and very pale blue tentacles with spots are on the back of her head. Her head has freckles; her mouth has sharp, jagged white teeth, and her tongue is pale, light grayish arctic blue. She has dark purple claws on her hands, while the claws her her feet are brown, the toes being pale, light grayish gamboge. The pin that Ivan gave her is attached next to one of her head tentacles, but is hidden by her slimy goo, which is akumatized.
After being reakumatized in "Catalyst", Horrificator's appearance remains the same, except most of her body is colored red.
Mylène wears an outfit similar to her regular clothes. However, her bandana is solid pink, her daisy pin has less petals, and she is missing the yellow and green pin and the panda pin.
Ivan gives Mylène a black pin with white skull crossbones on it to cheer her up after she gets scared during the class’ filming project. She wears it on her bandana.
To commemorate the celebration of Heroes' Day, Mylène wears a pin that has the French flag, with a blue and white silhouette of the French Imperial Eagle symbol.