To access the debug mode in King's Quest I to III, press Alt+D while playing. Two information boxes will appear. Press Enter to get rid of them. Now type in the following:
GIMME GIMME: Gives you all items in the game
TP: Changes rooms
ROOM: Displays room number
SHOW VAR: Show variable
CHANGE VAR: Changes variable
NOTE: If you use the versions that came with the KQ collections, then only the TP and SHOW VAR cheats work.
