Buffy the Vampire Slayer (1997)

S3E16 Doppelgangland

During a magical incantation, Anya and Willow inadvertently bring forth an evil version of Willow from a parallel universe. As the sinister double wreaks havoc, the duo must find a way to contain her and prevent chaos from spilling into their world. With time running out, Anya and Willow must confront the darker side of Willow’s personality, testing their friendship and magical skills in a battle against this formidable foe. Can they outsmart the evil doppelgänger before she takes over their lives?