Rear end pop/knock ?

[wytlytning]

I have a pop/ knock sound that is coming from the passenger side rear.
I can make it happen when taking a quick stab at the gas or brake. Even
if I hit the brake when the car is in neutral, like on a hill. The sound is coming from behind the rear seat bottom, like something is hitting the body. I can't seem to exactly locate it. Has anyone experienced this.
thanks.

 

[Dark Knight GT]

Some creeks, knocks, and pops are normal. However, if it keeps happening, its probably something loose or something moving around. Check your trunk and floor board to make sure you dont have any loose objects rolling about such as cans, bars, or anything of the sort. I would also give my car a quick look underneath to make sure you're not dragging anything.