Hobblegrunt

The Hobblegrunt is a Stoker Class dragon that made its debut in the movie, How to Train Your Dragon 2.

Official Description
"More sensitive than most other Stoker Class Dragons, it changes color depending on its mood: Yellow means happy, purple means curious, and red means... RUN! The Hobblegrunt will take on anything its opponent dishes out in combat, and then will dish it right back!"

- Dragons: Rise of Berk

Egg
In "Dragons: Rise of Berk", the egg of a Hobblegrunt has several ridges that look similar to the fins of an adult Hobblegrunt. It is unknown if the fins are for protection, or just appearance. They are usually found green. Gruff's egg, however, is purple with a lime green tip.

In "School of Dragons", the egg has different shades of brown and grey. They have several orange spots and a row of fin-like structures protruding from the top of it.

Hatchling to Adult
These dragons are colorful creatures. These dragons are bipedal, but they have two small forelimbs with long claws. They have long, thin necks, but surprisingly strong. Their heads are large, with a big jaw that has an underbite, showing all their many teeth. They have a small nose horn, at the front of their heads with their eyes just behind the horn. At the back of the skull, there is a massive fin that acts like a giant radar. They can move this fin to better observe their environment. Down their back they have short spikes. Their body is long, but their large tail helps them balance whilst on land. The tail ends in a fin that helps for stabilization during flight. It has clawed wings, small arms and big legs like a Deadly Nadder. It also appears to have long neck and tail as well. Its tail has frilled edges, similar to that of a Monstrous Nightmare. The Hobblegrunt doesn't have a particular color, but instead it changes color depending on its mood:
 * Yellow: Happy
 * Purple: Curious
 * Red: Angry

Titan Wing
Titan winged Hobblegrunts have a large frill with small 'horns' on its edges. It has two large pale pink spots on it. They are mainly light blue in color. Their neck is clearly segmented and their winks have pink rings on it. Additionally, these Titans have grown four small spikes on their long, slender tail and a sail-like fin on its back.

Behavior and Personality
Their primarily diet composes of fish.

These dragons are usually calm and sensitive they don't make too much noise, but when it senses an unpleasant atmosphere, it can become aggressive!

Color Changing
The Hobblegrunt is able to change its colors like a chameleon and even for similar reasons, contrary to popular belief chameleons change color to communicate and show their emotions, similarly to the Hobblegrunt, and this ability is similar to that of the Changewing. Instead of doing it for defensive purposes, it changes color depending on its mood. It can use this ability to calm other dragons.

Detecting Frill
Using the large frill on its head, the Hobblegrunt is able to detect the subtle shifts in temperature, barometric pressure, and the emotional states of nearby dragons or humans.

Hobblegrunts also have the ability of from frill to alter dragon's behavior in its vicinity, either to calm them, or rile them up in the face of a common enemy! It means, even if blinded, a Hobblegrunt can still navigate the terrain easily.

Weaknesses
The color changing properties of this dragon can allow hunters or foes to determine weaknesses or if it is aware or not.

Training
Since they can sense emotions, you have to be unafraid, yet show with your that you mean no harm, which makes it difficult if the Hobblegrunt in question is being threatening towards you. Of course coaxing with food helps too.

How to Train Your Dragon 2
Valka owns an adolescent Hobblegrunt named Gruff that was blinded by a tree snare trap and introduced it to Hiccup. Despite being blind, he still lives a happy life in Valka's Dragon Sanctuary. Several other Hobblegrunts are seen at Valka's Mountain.

Dragons: Rise of Berk
The dragon appeared in "Rise of Berk", along with Gruff and a Primal Hobblegrunt, which is a subject of the Bewilderbeast.

School of Dragons
The online game "School of Dragons" used the design and model of the Threadtail instead of an actual Hobblegrunt to create the dragon in-game.

Trivia

 * The Hobblegrunt is the second dragon species that is able to change its colors, with the first being the Changewing.
 * Although the 'Guide to the Dragons' stated that the Hobblegrunt was a Boulder Class dragon, the official website later revealed it was a Stoker Class dragon.
 * The Hobblegrunt is similar to the Mood-Dragon in the books.
 * According to Fishlegs' Dragon Stats, Hobblegrunts are, during the time of "How to Train Your Dragon 2", the newest addition to the Stoker class.
 * The Hobblegrunt is considered a good luck dragon as it is able to predict things a split second before they actually happen.
 * In "Rise of Berk", the Hobblegrunt is missing the frill on its tail and has an excessively long neck.
 * In "Rise of Berk" the Hobblegrunts eyes are completely white, this is a common mistake made by many people due to the fact that Valka's Hobblegrunt, Gruff, was the closest shot we got of the Hobblegrunt, when in fact white eyes are a feature unique to just Gruff due to his blindness, while usually Hobblegrunts have yellow eyes with pupils.
 * The Hobblegrunt was created using a modular system to mix and match preset body parts onto different dragons. It was created from the same base that was used for the Raincutter, Windstriker, Thornridge, Threadtail and two other unknown dragons.