I had no idea, but I guessed, and I was right. It is one of many slang expressions for smoking marijuana. In general, mysterious references to a) having crazy ideas and b) smoking, are often slang references to smoking marijuana. "The drapes" usually means "the curtains at a window." It is usually not worth trying to understand the origins of slang expressions.

It is slang...meaning that someone has been smoking marijuana or pot. There are a lot of slang words for marijuana. Hope that helps :)

PLL