First highlight the extra new game option.
Then press the following keys: W, W, S, S, Q, E, Q, E, Escape, Enter.

This only works if you haven't changed your key configurations, otherwise you'll have to find out the right buttons yourself.Now just choose the difficulty and the riddle level. You should hear Heather's sigh when you start the game and when you see Douglas he'll be wearing boxers and no pants