Walden and Alan throw a bachelor party for Marty once he proposes to Evelyn.
Provenza may be forced onto desk duty, the squad looks into the death of an ICE agent, and the squad meets peculiar residents of an apartment.
Molly is so focused on directing a school recital that she doesn't realize a fellow teacher is hitting on her. Meanwhile, Vince convinces Mike to join him in an unusual money-making scheme.
All the dragon species have multiple individuals except for Night Furies, Hiccup finds a secret page in the book of dragons revealing to him a secret island where other Night Furies live. Hiccup and Toothless embark on a challenging adventure to the island, but what may lie in his path, only one can guess.moreless
After Fishlegs find a rare gem, a group of Changewings follow him.
Toothless encounters a rival from his past. Blinded by their grudge against each other, Toothless runs away in hopes to battle the rival alone. Hiccup must find Toothless and reason with him before this rivalry turns fatal.moreless
Because the vikings' homes can't support the weight of the dragons, they install metal perches above the homes. However when lightning keeps striking the village, Toothless gets blamed for angering the god Thor.moreless
The annual Thawfest games are starting and this year dragon events are included, which means Hiccup finally has a chance to win.
The dragons become sick and the gang try to cure them.
Worried Stoick is disappointed in him, Hiccup heads out on a treasure hunt to prove his worth.
Hiccup convinces Stoick that riding a dragon would make his life easier and teaches him how using Toothless. However when Stoick overworks Toothless, they need to find him a dragon of his own.moreless
With the dragons gone, Alvin and the outcasts are poised to attack.
The dragons are falsely accused of vandalism and banished from Berk, leaving the island vulnerable to an attack by Alvin and the Outcasts.
While racing during "dragon boarding", Hiccup and Astrid cause an avalanche and end up buried in a gorge. With no one to help them, they realize they can trust the dragons to save them, but the farm animals are still too fearful. The trainers try to teach the animals to trust the dragons, however in the end it is the dragon's natural protective instincts that are key.moreless
With vikings and dragons now at peace, Gobber's role as weaponsmith is no longer needed. Hiccup tries to find him a new job.
Agatha's new beau brings a nosey playmate over for Rebound.
Mermaid Man Begins: We learn the origin story of the underwater superhero Mermaid Man and his sidekick Barnacle Boy.
Plankton's Good Eye: Plankton steals SpongeBob's DNA so he can grow a second eye, but Plankton having a second eye means that his personality changes.