Yesterday, the younger Sunday School group was doing the story of the Road to Emmaeus. There was a bread-tasting table, with different kinds of breads on it (naan, breadsticks, gluten-free lemon biscuits, matzoh, granary bread, etc.) and a table where they could make their own "road" by putting peanut butter or Nutella on a row of biscuits and covering them with "pebbles" (big sugar dots) or "dust" (brown sugar strands). They could then draw the rest of the scene on the paper plate.
But just as the storytelling was finishing - with the words, "Jesus is alive! We knew him in the breaking of the bread! Alleluia!" the main church had reached the Gospel acclamation, and the whole congregation sang out "Alleluia - Alleluia - Alleluia!" echoing the final word of the story.
You can't plan for this stuff - it has to just happen.