The Ugly Fish is a female fish who only appeared in the episode "Glove World R.I.P." In the episode, SpongeBob pretended to be a mirror by standing in a mirror frame and shapeshifting himself so he looked like whoever came up to it. When the Ugly fish came up to the mirror, she disliked her "reflection." She saw how ugly she was and knocked out SpongeBob.
She has wrinkly blue skin and wears an orange dress. She also has a small fruit bowl in her grey hair. Her eyes also appear to look in a different direction.
Due to her knocking out SpongeBob because of her appearance, Ugly Fish may not know what she really looks like herself, or is oblivious to her look.