"The thing I wonder about is where does Brian's creative spark come from? Not his subjects or anything, but his spark. What makes it so great for me is that I really don't know. There's a mystery behind Brian, even to me"

In this quote, Dennis Wilson expresses his interest about the source of Brian's creative motivation. He is not referring to the specific topics or styles that Brian selects to check out in his work, but rather the underlying trigger that drives his imagination. Wilson is interested by the reality that he can not identify exactly what makes Brian's creativity so exceptional. He sees a mysterious quality in Brian that even he, as a buddy, can not fully comprehend. This quote highlights the enigmatic nature of creativity and the awe it can inspire in those who witness it.