LT Crew Cab with no sunroof and I have the popping noise. It's completely random when it happens, to include having been sitting in my driveway turned off for a few hours. I just happened to be standing by the truck when it happened and it really sounded like it came from somewhere inside the third break light or the housing that runs the width of the cab. On that particular time it was in the evening and my guess was it had something to do with the temps cooling off since it was pretty hot that day. Inside the cab, it sounds like an acorn or pine cone hitting the top of my truck.
Took it to the dealer and got the normal "couldn't duplicate the problem" answer. I can't say for sure, but I think I heard it for the first time around 800-1,000 miles. Frequency doesn't seem to have changed any now that I'm at right at 2,000 miles. It may be 3x in one trip, or I may go 3 days without hearing it.
Subbing to the post in case someone finds a solution.