They often sing when they gather in large groups. A "singing" Terrible Terror also appeared in "Fright of Passage", where Snotlout had to deliver the Twins a singing Terrible Terror. In How to Train Your Dragon 2, Hiccup mentions he had been woken up by Terrible Terrors singing on his...
One good question to ask is, do we like him? And I think Cameron does a good job of getting us to like Jake. We learn about his disability (he's in a wheelchair), and the surprising accident that led to restoring his legs. He's a tough, kind guy who is getting a lucky break....