Drutt is a grey, blob-shaped bug that appears in The Trap Door. He is Berk's irritating and useless pet and does little around the castle other than chase and gobble down worms and get in Berk's way when he's busy. He constantly makes strange squeaking noises which tend to grate on Berk's nerves.
In later episodes of The Trap Door, Drutt is shown to have a family. His babies - which Berk calls "nippers" - are just as irritating and stupid as Drutt himself.