The preview for Pokemon Detective Pikachu shows the character covered in thick yellow fur, which some fans have called "grotesque" and "disgusting".
While Pikachu has always been described as furry, it is the first time the character has been rendered in "life-like" 3D in an official capacity.
Many fans liked the realistic fur.
Pikachu appeared in the first Pokemon game, which was released in Japan in 1996.
It quickly became a global phenomenon and has become one of the best-selling entertainment franchises of all time.
Pikachu is an electric mouse and the animation series has previously showed the character with hair, albeit in a stylised and undefined way.
The new Warner Bros film is the first official movie to integrate Pokemon characters in real-world settings with actors.
Deadpool actor Ryan Reynolds provides the voice for Pikachu, which has historically been voiced by Japanese actress Ikue Otani.
While many fans questioned the hyper-realistic art style of the film, others pointed out that it reflected what Pokemon might look like in real life.
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