Odd prop in a realistic movie: the rock in Joon-ho Bong's Mother

I'm a big fan of the South Korean director/writer Joon-ho Bong.  Last night I watched his most recent movie, Mother.

Excellent, like all of his movies, though I still think Memories of Murder is my favorite.  Mother has some themes in common with that earlier murder investigation movie: lazy, incompetent cops; corrupt late-middle-aged upper class males (in this case a delightfully self-absorbed lawyer and some pompous professors); too-knowing schoolchildren; and a tattered semi-urban landscape of small shops, government offices, and piled-together dwellings.

I won't detail the plot, which intense and creepy.  I'll just mention something I found truly odd.  A rock plays a significant role in the narrative. A big rock.  A boulder, in fact. The thing probably weighs eighty pounds, but people, including a small adolescent girl, toss it around like a brick. It's almost magic realist, particularly given the rest of the movie's careful realism.

I remember being struck by a scene in the postwar movie Best Years of Our Lives. Dana Andrews, as a returning serviceman having trouble readjusting to civilian life, punches somebody out in a department store. The guy falls onto a display case--which shatters into a thousand pieces, as Hollywood props always do.  Nothing bursts into flame, but, again, the movie was determinedly realistic aside from this one bit of absurd prop work.

Physical reality in movies is always way more plastic than it is in real life, often so something "reads" in a way that can quicly be identified, with smashing objects standing in for the bodily damage a movie can't effectively show. Still, the easily tossed boulder tossed me out of an otherwise compelling movie for a few moments.  I still think it was an odd and unnecessary choice.