Personally, this one is tied for their follow-up hit "Attack" as my favorite song from the toys.... heck, I bought their only LP at my local thrift store for only one dollar on the day they re-opened under new management!!!!
As a kid I just loved this song, totally unaware of the fact that it was based on a gorgeous Bach melody. Later still, I realized it was the four key changes that made it sound so incredibly vibrant. Amazing how the girls handled it with such apparent ease.