- , , and : By default, use these four keys to make Berk walk up, down, left and right, along with to make him drop the objects he has picked up and tip out their contents; however, if you press on the start screen to redefine these, they can get changed to anything you want. You can also press to pause the game and to resume it, or (on the start screen) to switch control to a Kempston joystick (if connected).
This friendly blue creature (who is a darker shade of blue than he was for the show) is the protagonist of this game (and overworked servant of the Thing Upstairs); at the start of the game, you can choose to be a "Learner Berk" or a "Super Berk", and if it is your first time playing, it is advisable to select the former mode (on account of how it is easier, even if you will not earn as many points or Berk's pay). Underneath the eponymous trap door, all kinds of monsters are waiting to escape as soon as it is opened - and most of them have useful roles in completing Berk's tasks but the real task is knowing which monster is needed for a specific task. If a wrong monster escapes, Berk shall have to get it back down the trap door as quickly as he can; also, if the trap door is left open, hungry spooks shall emerge from it and the only way Berk can get rid of them is by feeding them (as like Namco's Pac-Man, they shall eat anything). However, in "Learner" mode, the spooks will have gone on holiday - and all the props required for the tasks can be found in the basement of the castle, but it may take some time to work out how to use them. The "Anger-Meter" at the bottom of the screen shows how long Berk has to complete his current task; if it runs out, The Thing Upstairs shall yell to Berk that his time is up (and a new task will be set). However, once Berk has completed all the tasks, the Thing will send down his wages, in a tough-looking safe - and in order to get them and become a true Super Berk, he'll have to open it. Once he has done so, the text "AS A SUPER BERK I RATE YOU AS...CLEVER AND OVERPAID" will appear.
Boni and Drutt
Boni is Berk's friend and Drutt is Berk's pet, the former being a long-suffering and wise old skull (shown in the image to the left) and the latter being a gray spider who sounded like Nero from Cosgrove-Hall's Danger Mouse (however, due to technical limitations, he is depicted as yellow in the game, as shown in the image to the right); each time Berk picks Boni up, he shall say a few words, often giving useful advice on how to complete a task. However, Drutt will hop around getting in Berk's way and eating worms (which can make it harder to complete the "Can of Worms" task) - but for the "Tidying Up" task, Berk will have to send them both down the trap door, along with the worms for the "Can of Worms" task, the pots used to grow the eyeball plants in the "Crushed Eyeballs" task, and the vat for that very same task. Drutt also later went on to become a playable character in Through the Trap Door in 1987.