The green door appeared to Wallace when it does as it reminded him of a place that he can escape to and where he'll find happiness.
The green door in the story represented the passageway between the conscious and the unconscious. Anytime Wallace entered the <em>green door,</em> he felt a sense of happiness and well-being.
When Wallace woke up, he was back on the miserable streets of West Kensington. The door was a source of hope and happiness to Wallace.
