In the Books
Speedifist is introduced in "How to Train Your Dragon" (Book 1). He is known to be the fastest Viking novice, as well as an excellent warrior. He has an Eaglefly for a Hunting Dragon and for riding a very fast Swiftglider. He is best friends with Tuffnut Junior. Speedifist is also the only known "non-stereotypical"-featured Viking.
In School of Dragons (game)
Speedifist also makes an appearance in School of Dragons along with Clueless and Wartihog from the Book Series. During one of the quests the player is required to speak to Speedifist and retrieve notes from him for the Headmaster. Speedifist can be found standing outside the Thunder Run. This version of Speedifist has a much different appearance, than Speedifist of the Books.