- "I have one," grinned Snotlout, gesturing to the terrifying-looking, flame-red animal fast asleep in his basket. "I think I shall call her FIREWORM."
- ―How to Train Your Dragon
Ownership and Training
Fireworm sniffs out Grimbeard the Ghastly's false treasure he buried on the isle of Skullions. She is also one of the first dragons to smell the malodorous boovy-trap in the treasure chest, and retches in the heather.
Hunting Dragons seem to accompany their masters everywhere they go, including classes. While waiting for Gobber to appear in the Great Hall for a 'Frightening Foreigners' lesson, Snotlout, Dogsbreath, and Fireworm harass Fishlegs.
- "Snotlout and Dogsbreath the Duhbrain were sitting on Fishlegs while Fireworm set fire to a pile of Fishleg's workbooks."
- ―Book 3
Fireworm is a large young Monstrous Nightmare specimen with bright flame-colored scales.
Fireworm is very vain and thinks highly of herself amongst dragons, even other Nightmares. She has great physical prowess. She shows no one loyalty, only when it is for her benefit. She does to brave deeds, but again only if those deeds pay off for the winning side. She also loves to sneer about stuff she hates, like Toothless.
- "That's not a dragon ... that's an ickle newborn bunny wabbit with a pathetic poo problem."
- ―Book 1
- "That creature [Toothless] was a disgrace to us green-blooded FireBrothers of the Snake."
- ―Book 3
|"How to Train Your Dragon":||Appears||"How to Ride a Dragon's Storm":||Absent|
|"How to Be a Pirate":||Appears||"How to Break a Dragon's Heart":||Absent|
|"How to Speak Dragonese":||Appears||"How to Steal a Dragon's Sword":||Absent|
|"How to Cheat a Dragon's Curse":||Absent||"How to Seize a Dragon's Jewel":||Absent|
|"How to Twist a Dragon's Tale":||Absent||"How to Betray a Dragon's Hero":||Absent|
|"A Hero's Guide to Deadly Dragons":||Absent||"How to Fight a Dragon's Fury":||Absent|
- Fireworm makes no appearance in the film; however, a Monstrous Nightmare named Hookfang is trained by Snotlout. Hookfang is the name of Stoick's in the books. Unlike his Fireworm, Hookfang is male and has a very different personality. Unlike Hookfang, Fireworm is very obedient towards Snotlout. Hookfang in the movie seems to show grudging respect towards Hiccup, whereas Fireworm in the book shows as much animosity as her owner towards him.