At the scene where Darla and Alfalfa are in the club house you see Frogman take the grape juice bottle and pours the sneaker crap in it. Notice that he puts it in front of the window he took it from. When Alfalfa picks it up, it's beside him and you can see the window behind him. Then when it shows Spankys view of the bottle,it is right behind Alfalfa, cause Alfalfa put it back beside him after they were done.