Episode Title:The Zippleback Experience.Episode Description:The twins start an avalanche on the island where the riders are setting up a new watchtower and Hiccup and Toothless save Barf and Belch before they can go over a cliff. As a result, Barf and Belch become indebted to Hiccup and relentlessly follow him around and dote on him, prompting the twins to come up with ways to put Hiccup in danger so their Zippleback will save him and return to them. Hiccup is captured by Ryker and Dagur but is rescued by Barf and Belch who in turn are rescued from drowning by the twins, repaying the debt and returning everything to normal.