They are pan-fried diced potatoes sold by the Krusty Krab, and have an oval-like shape. They come in a small white box with the Krusty Krab's initials imprinted in dark red text.
Role in episode
SpongeBob is at Patrick's house, demanding him to insert the vacation slides into the projector. Patrick agrees to do so and pulls out what he thinks are the slides, only for them to turn out to be hash browns. Patrick then proceeds to eat them and pull out the actual vacation slides from his belly button.
Although they are not explicitly mentioned to be sold by the Krusty Krab in the episode, the "KK" text on the box suggests that the restaurant does indeed sell them.
Despite the Krusty Krab selling hash browns, the Galley Grub is not shown to have a breakfast menu.
They are the only known breakfast item sold by the Krusty Krab.