The Thing Upstairs is a major but ultimately unseen character in the claymation series The Trapdoor - an evil and eternally hungry demon The Thing Upstairs is the master of the protagonist Berk and has the monster do all manner of tasks, first and foremost amongst them being feeding him.
It was voiced by Nick Shipley.
The Thing Upstairs resides within a massive and evil-looking castle and as mentioned above the demon is obsessed with eating - however his "food" is often vile and grotesque, such as worms or similar. There have even been occasions where Berk has feed monsters who emerge from the titular Trapdoor to The Thing Upstairs.
The Thing Upstairs is also a slave-driver who has Berk do other tasks around the castle. It is very apparent that Berk fears The Thing Upstairs as every time the demon yells out orders, Berk is quick to try and appease him. Likewise it seems even the horrible monsters that emerge from the Trap Door fear the Thing Upstairs, such as in one episode when Berk's radio causes nearly all of them to climb out, they all run back down the Trap Door when the Thing Upstairs starts shouting at the racket.