Monster Donut is a chain of doughnut shops across the @United States. On the stores' marquis, in huge black letters it said: "MONSTER DONUT". A cartoon ogre took a bite out of the O in MONSTER.

The shops are connected with the life force of the @Hydra and many other monsters. This was stated by @Annabeth Chase as being the reason some stores pop up so fast. This trick was discovered by some children of @Hermes in the late 1950s. Another Monster Donut shop pops up somewhere every time the Hydra grows two heads (after losing one). It also seems to be magic as the shops grow out of thin air, and @Tyson thought that their doughnuts were exceptionally good.

History

Quest for the Golden Fleece

After @Percy Jackson, Annabeth, and Tyson escape the Princess Andromeda, they hide in the @James River Safehouse, created in the days when Annabeth, @Thalia Grace, and @Luke Castellan were on the run. Wanting some privacy with Annabeth, Percy sarcastically tells Tyson to go out and grab some powdered doughnuts. They are surprised when he comes back with a box of doughnuts, claiming that he found them fifty feet from their hideout. They went to explore the area and see that there is a Monster Donut shop nearby, making Annabeth very worried. The parking lot was empty and connecting to a little road leading off into the forest, but there didn't appear to be any other buildings for miles. A cashier that looked like a human was reading a magazine, Percy could smell delicious chocolate donuts from inside. Apparently, only monsters are able to purchase the doughnuts (which is the reason why Tyson was able to do so) while demigods are killed and it appears partly because Tyson wished it.

The Hydra connected to Monster Donut eventually appears and attacks the trio. After Percy cuts off one of the Hydra's heads with @Riptide, Annabeth tells him that another Monster Donut just appeared somewhere else. They are saved by @Clarisse La Rue, who uses a cannon from the Confederate Ironclad battleship, CSS Birmingham, to slay the Hydra. They boarded the ship leaving the donut shop behind.

Quest for the Athena Parthenos

Monster Donut sponsors a section of the @Georgia Aquarium owned by @Keto and @Phorcys. While Percy Jackson, @Gleeson Hedge, and @Frank Zhang are being given a tour by Kate, Percy saw a red sign which he had to read twice because of his dyslexia which said this section was sponsored by them, reminding Percy of the first time he had to fight the Hydra. Later, doughnut-shaped circles that smelled like doughnuts made out of smoke appeared when they escaped from Phorcys and Keto.