As Haru enters in the Cat Kingdom (The Cat Returns) she slowly begins to turn into a cat.
As a goddess level sorceress, Circe (DC Comics) could to turn objects and people alike into various sorts of animals.
Principal Torres (Every Witch Way) turns Lily Archer into a frog
Diego Brando's Stand, Scary Monsters (JoJo's Bizarre Adventure Part VII: Steel Ball Run) turn victims into dinosaurs.
Loco (Marchen Awakens Romance) can use her Darkness ÄRM, Animal Chain to turn a person into any animal.
Irene Belserion (Fairy Tail) can turn other people into animals, such as when she transformed Princess Hisui into a mouse.
Babbo is turned into a cat guardian when Ginta (Marchen Awakens Romance) activates Version 6 - Puss in Boots.
SMILEs (One Piece)
Dr. Facilier (The Princess and the Frog)
The Cranky Wizard (Samurai Jack) unleashes a transformative blast that turns victims into chickens.
SCP-2746 - ████ is dead (SCP Foundation) is a portal between an underground tunnel in Las Vegas and an alternate dimension (SCP-2746-1) that transforms humans who travel through it into animals.
SCP-4670 - Pigs in Blankets (SCP Foundation) is a former serial killer who can turn humans into pigs, an ability she used on several police officers in order to butcher and cook them, and then serve their carcasses in her BBQ restaurant.