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.
Horrificator is a large salamander-like monster, the top half of her body mainly pink and the bottom half, along with her forearms, mainly purple. She has three yellow eyes with red pupils, the third eye being in the middle of her forehead, and periwinkle 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 light blue. She has dark purple claws on her hands, while the claws her her feet are brown, the toes being tan-colored. Also, she has a long purple tail. The pin that Ivan gave her is attached next to one of her head tentacles, but is hidden by her pink goo.