The Diner is a boat-shaped restaurant that has been known to serve milk, hot chocolate, coffee, and other foods. It makes its first appearance in "Mermaid Man and Barnacle Boy II."
The diner looks like a boat with two glass doors in front and a life saver. Next to the boat are some coral in barrels and on the sides of the diner are three windows on each side, and on the back is a blue flag. On the boat the word "diner" is inscribed in blue.
On one side of the diner, there are several tables and seats. On the other side is a counter and single-person seats. The kitchen is unseen, but there is a window like the one in the Krusty Krab where orders and dishes are exchanged. A jukebox is found at the end of the restaurant.
In its first appearance in "Mermaid Man and Barnacle Boy II," Mermaid Man and Barnacle Boy have lunch with SpongeBob here. SpongeBob asks them what they are going to tomorrow. Barnacle Boy tells him to take his nickel and look for the their theme song in the jukebox. While SpongeBob looks for the song, Mermaid Man and Barnacle Boy decides to ditch him. They go to the Invisible Boatmobile, however they get caught and trapped by the Dirty Bubble. SpongeBob finds the song and goes back to the table, only see Mermaid Man and Barnacle Boy trapped by the Dirty Bubble through the window. SpongeBob then goes outside of the Diner and pops the Dirty Bubble with a pencil.
In "Chocolate with Nuts," its role in the episode serves as a place for SpongeBob and Patrick to discuss about how they could become successful. Inside, SpongeBob and Patrick were talking about certain tactics about how to be successful. Even though their tactics discussed in the Diner didn't help give as much inspiration as meeting the Barnacle Chips billboard, their discussions did help somehow in becoming more successful.
In "Missing Identity," its role in the episode was the place where SpongeBob told his story about missing his name tag, and how he and Patrick had to find his name tag before a health inspection to a waitress, chef, and a fellow customer.
In "SpongeHenge," Shubie and Nat Peterson walk out of the Diner with a bag of leftovers. However, a windstorm blew the bag of leftovers away from her, and eventually hitting SpongeBob in the face.