The Viking town of Berk, now enjoying its new alliance with the dragons, is preparing for its annual winter holiday of Snoggletog. However, that spirit is threatened when all the dragons, except Toothless who needs Hiccup to help him, suddenly fly away for some reason. While Astrid ineffectually tries to salvage the occasion, Hiccup decides to build Toothless a new prosthetic to allow him to fly independently, only to have the dragon take off as well. However, as the holiday approaches, Hiccup finds himself swept up to learn the dragons' secret the hard way and to find a solution to bring them home early.

Dot, an Australian girl, seeks the magical green root that will give her the ability to talk to animals. She eats a red root by mistake, and is shrunk to the size of an ant. With the help of her friends Keeto the mosquito and Butterwalk the caterpillar, she searches for the green root that will restore her size. But she must find it before sundown, or she will shrink even smaller.

Leafie is a hen who manages to escape the horrible conditions of an egg production line. After surviving a harrowing encounter with a one-eyed weasel and being rejected by the barnyard animals where she grew up, a chance encounter sees her becoming the guardian of a duckling.  Despite the child being a duck, Leafie is willing to learn and make the sacrifices she needs in order to ensure the happiness of her son.

Ruled by King Augustin, Carpia is a peaceful kingdom in a world inhabited by dragons and knights. The land's serenity is unexpectedly shattered by a Fire Dragon that spreads almighty fear and death amongst the kingdom's innocent people.

Based on elements from the stories of Mark Twain, this feature-length Claymation fantasy follows the adventures of Tom Sawyer, Becky Thatcher and Huck Finn as they stowaway aboard the interplanetary balloon of Mark Twain. Twain, disgusted with the human race, is intent upon finding Halley's Comet and crashing into it, achieving his "destiny." It's up to Tom, Becky, and Huck to convince him that his judgment is wrong and that he still has much to offer humanity that might make a difference. Their efforts aren't just charitable; if they fail, they will share Twain's fate. Along the way, they use a magical time portal to get a detailed overview of the Twain philosophy, observing the "historical" events that inspired his works.