Apples appear in the background in various media in the How to Train Your Dragon Franchise.
Apples are the fruit of the apple tree in the Genus Malus. This genus can include the larger sweet apples that are widely cultivated, or other species with smaller more sour fruits referred to as "crabapples". Apple trees are mid-size deciduous trees that actually belong in the rose Family (Rosaceae).
The main function in both reality and the Franchise for the apple is food. It can be eaten raw or cooked and preserved in a variety of ways. Even the wood of the apple tree emits a pleasant smell when burned and is used to impart different flavors to smoked foods. In "How to Start a Dragon Academy", a dragon is seen stealing a bag of apples, indicating that dragons probably like to eat apples, too. Stormfly is seen eating an entire cart of apples in "Living on the Edge".
The apple also figures into several cultures' mythologies, including Norse. The Goddess Idunn is said to give out apples daily to the Gods that keep them youthful.
In the episode, "How to Start a Dragon Academy", the dragons are running amok in the village of Berk, breaking things and stealing food. A Monstrous Nightmare steals a bag of apples from a village man, yanking it from his hands.
In "Midnight Scrum" Hiccup gets chased by various bounty hunters on an Unnamed Island. Astrid and Toothless hear his call for aid. Toothless drops the bucket of apples he had collected and rushes to his rider's side.
Apples are seen as background objects again in "Saving Shattermaster", with an apple cart chock full of red apples.
An apple cart is also seen briefly in "The Longest Day".
In "Dire Straits", when the trading lanes are compromised by Viggo and his Submaripper, Berk is forced to ration food until trade finds its way to the island again. Bushels of apples are among the food passed out to hungry villagers. At one point, Hiccup shows compassion toward a hungry little boy by taking an apple out of Snotlout's hands and giving it to the youngster instead.
A cart of apples appears again being pushed by an Outcast on Outcast Island in "Return of Thor Bonecrusher". Thor Bonecrusher (Fishlegs) waggles his fingers at the man and he nearly swoons, allowing the apple cart to roll away. This implies apples can be grown on Outcast Island.
Apples appear briefly again, in the background, at the Northern Markets in "Sins of the Past".
An apple cart appears in the episode, "In Plain Sight".
Apples also appear in "Triple Cross" when Ruffnut and Tuffnut fill up Barf and Belch's mouths with apples and then try to smash them. The dragon instead spits them out everywhere. Later in the same episode, Barf and Belch rain down flaming apples on Johann and the Dragon Hunters.
Apples appear in the player quest "Prepare for the Big One!", in which the player must collect apples in the Wilderness area of the School of Dragons Island.
Images of apples appear in Loki's Maze of Cheers during a labyrinth part.
A bag of apples is a collectible item that can be bought from Johann in order to complete collections.