Summary from Wikipedia):
The Trap Door is a computer game published by Piranha, for several 8-bit formats in 1986. It was written by Don Priestley and based on the British children's television show of the same name.
The player takes control of Berk, who must perform tasks for "The Thing Upstairs" a never-seen entity who lives in the upper floors of the castle where Berk works. In order to help him complete his task, Berk must make use of the many objects lying around his part of the castle as well as the creatures that emerge from the trap door. Berk is assisted by Boni, a talking skull, who provides hints when picked up. He is also somewhat hindered by Drutt, a yellow two-legged spider who loves eating worms.
Source: Wikipedia, "The_Trap_Door_(video_game)," available under the CC-BY-SA License.