In the “Dune” movies, a gigantic sandworm can rise from the desert and devour soldiers and military vehicles in its gaping maw. In real life, humans watching movies devour popcorn. These two ideas have been combined to spawn the “Dune” popcorn bucket, a sandworm-shaped tub that is having a cultural moment. The bucket arrives on the heels of other recent popcorn collectibles, like the 16-inch Barbie Corvette snack holder. But is there more to these vessels than meets the eye?