While Astrid, Snotlout and the rest of the gang are challenging each other to dragon races, Hiccup and Toothless journey through the skies, charting unmapped territories and exploring new worlds. When one of their adventures leads to the discovery of a secret ice cave that is home to hundreds of new wild dragons and the mysterious Dragon Rider, the two friends find themselves at the center of a battle to protect the peace.

When Lilo and Nani go to the shelter to adopt a dog, they come home with an extra-terrestrial fugitive; a glitch in experiment 626 otherwise known as Stitch has him turning evil again despite his high goodness level, and it is now up to Lilo to find the cause and make sure that Stitch continues to be good.