Incidental 157, also known as Fish F is the name of a group of four anchovies who appear as background characters in the series. They first appear in the episode "F.U.N."
They are four anchovies dressed for work. They all wear long-sleeved shirts, neckties, striped pants, and black shoes. On their model sheet, there are four anchovies, from left to right:
Green with a blue tie, blue shirt, and blue pants
Tan-brown with a teal tie, yellow shirt, and green pants
Orange with a red tie, white shirt, and blue pants
Tan-brown with a lavender tie, off-white shirt, and gray pants
Their appearance and number of members changes depending on the episode. Sometimes, they also wear hats or fedoras. In several episodes, the anchovies' skin is changed to blue and brown but they retain their clothes' usual colors.
Three of them are seen at the Krusty Krab eating together, with another one waiting in line, but they later head to the Chum Bucket when one of Plankton's fake fortune cookies reads that they would live forever if they eat there.