Mylène Haprèle, known as Polymouse is one of the supporting characters of Miraculous: Tales of Ladybug & Cat Noir.
She is dating Ivan.
In "Horrificator", she is corrupted by Hawk Moth into the titular supervillain that grows more powerful the more feared she is.
In "Mega Leech", Ladybug gives the Mouse Miraculous to Myléne to help defeat André Bourgeois, who has been transformed by Hawk Moth into Malediktator again. She meet Mullo, the mouse kwami, and transforms into Polymouse for the first time.
Mylène is a meek and cordial girl. Although she tries to be brave, she is easily frightened by anything that she sees as scary, which she is ashamed of and even cries about in "Horrificator". She also is sensitive to being made fun of and is hurt by Chloé's mean remarks about her. She appreciates kindness, and she speaks very fondly of those she loves. According to Marinette in the webisode with the same name, Mylène always tries to look for the best in people.
As Horrificator, she relishes in making everyone scared (as opposed to her being scared). Aggressive and menacing, she attacks everyone and doesn't like it if any of them aren't freaked out by her. Despite this, she retains her feelings towards Ivan and refuses to harm him. When she is calmed down, by the song Smelly Wolf, her bravado and confidence are gone, leaving her terrified by the others and running into Ivan's arm for comfort and protection.
As a result, she is given a pendant necklace known as the Mouse Miraculous.
- Shrinking replication: her special power, Multitude, allows her to make small copies of herself.
- Nigh-invulnerability: she is also invulnerable to almost any injury in her transformed state.
- Fear absorption: she can absorb the fear around her.
- Size-shifting: she gets bigger when others are non-verbally scared of her. But when someone doesn't show any sign of fear, she gets smaller.
- Enhanced strength: while she's big, her strength is increased.
- Goo breath: she can spit goo from her mouth that hardens like cement.
- Prehensile tail: she can also use her tail to grab her victims.
- As of Season 4, Mylene is the second known person of French origins to wield the Mouse Miraculous succeeding Marinette Dupain-Cheng.
- Her voice actress, Jessica Gee also voices Tria from The Land Before Time, Sakura Ogami from Danganronpa: Trigger Happy Havoc.