It is said that when one sister marries evil, she turns evil before it spreads to the other sisters and the book. Later, when Phoebe marries Cole, she doesn't even know it at first. Then after she accepts it, Piper and Paige never turn evil.
The light blue frilly top that Piper is wearing is the same top that she refuses to wear in a later series when she buys maternity clothes during her pregnancy with Wyatt.
When the dark priestess Dantalian is knocked down by Phoebe, she is wearing boots, but in the next shot she's wearing high-heeled shoes.