Generally it's not considered a compliment when a shot looks fantastic and the AD says "now that's a happy accident". It negates any skill or expertise we stylist bring to the table.
That said, I had my own happy accident the other day. I wanted to do something just a bit elevated from the standard water bottle on white seamless. White plexi was the plan, but then at Cliffs Variety I spied this clear sheet vinyl and thought I'd give it a try. So, although the shot is still just a shot of water bottles on white, it has just a hint of water and wet from the vinyl. And it cost a lot less. #Happy Accident.