Hiccup's Prosthetic Leg

Hiccup lost the lower half of his left leg in the battle against the Red Death. Gobber made him this leg, "with a little Hiccup flair thrown in" along with Toothless' new tail.

Gift of the Night Fury
By this time, Hiccup has gotten used to his new leg, but still slips on the ice, in fact, he does it twice. Toothless is usually there to catch him.

Riders of Berk
Hiccup's leg is occansionally poked at in the series:


 * In Portait of Hiccup as a Buff Young Man, he uses his leg to grab the second key in a rock formation of a serpent.
 * Midway into Twinsanity, Dagur the Deranged notices Hiccup's leg and questions him on how he lost it, referencing his battle with the Red Death.


 * Snotlout appears to be a bit jealous of Hiccup's missing limb, as shown in Defiant One.


 * A Smothering Smokebreath targets Hiccup's leg and nearly causes him and Toothless to crash near the end of Breakneck Bog.


 * In We Are Family Part II, he takes off his leg to use it to knock out the Outcast guard, but doesn't quite work out like he planned.

Defenders of Berk

 * In The Iron Gronckle, Hiccup got stuck to Meatlug because of his metal leg. He was later freed by Fishlegs, who was riding Toothless.
 * In A View To A Skrill Part I, when Hiccup voices his intention of going after the Skrill, Astrid tells him to be careful, reminding him that he and Toothless are wearing a lot more metal (which lightning is attracted to) than all the rest of them. In A View To A Skrill Part II, Hiccup references this briefly during a thunderstorm when he tells Toothless to watch his tail while he watched his leg.
 * In Free Scauldy, Ruffnut pretends to be Hiccup for a few minutes to entertain Scauldy; she takes a creative approach to how the old leg had disappeared, claiming that it "fell off."
 * The metal leg is only referenced once in Frozen, when a Speed Stinger tries to stab Hiccup with its tail and finds itself foiled; Hiccup laughs that they "never expect the metal leg!"
 * Although the metal leg itself is not referenced in The Eel Effect, the fact that Hiccup only has one good leg left is mentioned when a sick Toothless nearly blasts it.
 * In Smoke Gets in Your Eyes, the juvenile Smothering Smokebreaths target Hiccup's prosthetic leg twice (the first time gets them discovered). Between those times, when the dragon-riding teens make the decision to bait the Smokebreaths in order to follow them, Snotlout wants Hiccup to add the leg to their pile instead of his spare helmet (and was voted down because Hiccup needed his leg both to walk and to help Toothless fly).

HTTYD 2
Hiccup has a new modified leg in the second film. Dean DeBlois decribes it as the "Swiss army knife of prosthetics."

Trivia

 * In the video game Hiccup has two good legs.
 * The loss of his leg makes Hiccup the youngest Berkian to have a prosthetic limb.