The Angel & Devil Doughnuts were two doughnuts who made a minor appearance in the episode, "The Donut of Shame."
The Angel Doughnut
The Angel Doughnut is a white doughnut with white frosting, golden sprinkles, angel wings, and a halo, giving Patrick good ideas.
The Devil Doughnut
The Devil Doughnut is a red doughnut, with red frosting, devil horns, and a red tail, who gives Patrick bad ideas.
The Angel & Devil Doughnut appear after Patrick steals SpongeBob's doughnut and interrogate Patrick of his actions. They appear to act like his conscience. The Angel Doughnut tries to stop Patrick from hiding the doughnut from SpongeBob, while the Devil Doughnut tells Patrick to not listen to the Angel Doughnut because "he's covered with sprinkles." The Devil Doughnut devises a plan in which Patrick hooks the doughnut to a chain, eats it, and can pull it back up with the aforementioned chain before SpongeBob finds out what happened. The Angel Doughnut admits that it was a good idea after the Devil Doughnut explains the plan. This plan, however, failed. When Patrick pulled the chain out of his mouth, the doughnut was no longer attached to the chain.
This is reminiscent of popular media where a character's conscience (i.e: Good, telling good advice and Evil, telling bad advice) tells the character what to do in a certain situation.