Best guess: They got three similar looking girls and dressed them up the same so you wouldn't be able to tell them apart from a distance. Under each barrel is a trap door. The top part of that wagon that the barrel sits on is like a coffin, just big enough for one person. At the end of the trick, when they're removing the wagons one by one, they remove the one with the original Stacy first so she can go back to where she was.
How did they do this?
Best guess:
They got three similar looking girls and dressed them up the same so you wouldn't be able to tell them apart from a distance. Under each barrel is a trap door. The top part of that wagon that the barrel sits on is like a coffin, just big enough for one person.
At the end of the trick, when they're removing the wagons one by one, they remove the one with the original Stacy first so she can go back to where she was.