Stump Day is a holiday mentioned by Gobber and Mulch in the episode We Are Family, Part 1.
History
Gobber is preparing for Bork Week, and excitedly exclaims the festivities of Bork Week are right up there with Stump Day. Mulch agrees, and the two men give each other "high-fives" with their prosthetic arms.
Not much is known about this event, except that it is a celebration for those with prosthetic arms and legs.
Trivia
- It is possible Hiccup could celebrate this event, because of his missing leg.