Incidental 12 is a fish who makes a lot of cameo appearances throughout the series, starting in the episode "Ripped Pants." She is Incidental 13's wife.
She is a light purple fish who has light blue eyes and black pupils. She also has an orange dorsal fin. She wears a red bathing suit and pink lipstick.
In the book adaptation of "Hall Monitor," she has a different appearance. Her eyes are both on the front of her head and she wears a curled wig and a ruffled shirt.
- ^ Incidental Model Sheet 1