I was there when they made the track for that sound. What they did, they got 11 babies, about 8-10 mos old, gave them spoons and glass jars. They glued the jars to their feeding trays with Superglue for safetly. Then they got their moms to encourage them to bang on the jars with the spoons. The first attempt had the right amount of haphazardness to it, but it was a little thin, so we recorded the track over itself with a 17 millisecond delay a couple times. Then the sound engineer speeded it up to raise the speed and pitch, and it was done.