The Catfishstress is a one-time villain from the Spongebob Squarepants comics. She appeared in the comic book issue, "Claws of the Catfishstress". She is a female catfish with a mustache, who's in love with Mermaid Man and wants to convert him to evil and make him her lover/partner in crime.
In "Claws of the Catfishstress", Catfishstress kidnapped a young Mermaid Man and tied him to a pole, preparing to turn him into a villain just like her. In his head, Mermaid Man was battling with his romantic feelings for Catfishstress.
Barnacle Boy hid behind a rock and watched Catfishstress caress Mermaid Man. Apparently, Mermaid Man had previously pushed Barnacle Boy away because Catfishstress manipulated him into doing so. Barnacle Boy still stayed faithful to Mermaid Man and went to save him.
Barnacle Boy sprung into action and started fighting Catfishstress. The Catfishstress tried to whip Barnacle Boy, telling him that Mermaid Man was her partner now. However, Barnacle Boy grabbed her whip and tied her up with it, using her own weapon against her. With Catfishstress immobilized, Barnacle Boy seized the opportunity to set Mermaid Man free.
Mermaid Man and Barnacle Boy felt the need to comment on The Catfishstress' mustache, saying how weird it was for a girl to have a mustache as part of her mask. Barnacle Boy removed The Catfishstress' mask, revealing that her mustache was not actually part of her mask but part of her actual face, which freaked both of them out. Mermaid Man fell out of love with Catfishstress at this point and the duo flew away.