IO9 dangles this tantalizing possibility:
They were filming a scene in the hospital where the Kents were taking a young Clark in for a checkup. Kevin Costner was on set, as well as two boys who were playing young Superman. The scene included breaking of windows on the front of the building, a fish tank, a gumball machine, a mug as well as windows on the Green 1970 Nova and the station wagon all as a result of young Superman letting out a Super Cry.”
Read the full piece here.