Season 4, was very much a 'make or break' time for Charmed with the introduction of new sister Paige. In my opinion this is one of the episodes that helped Season 4 land on its feet.
Watching Paige go back to the day her adoptive parents died was very revealing about her character, her teenage self very much being portrayed as a 'rebel' who caused her parents all sorts of trouble. I found it amusing that all that was needed to transform Paige back into a teenager was a change in costume and the addition of braces.
Paige's part of the episode was touching and also heartbreaking, seeing her desperate attempts to change the past and prevent her parents' death, but nevertheless revealing as it turns out that it was her whitelighter half that saved her that day.
The comic relief in this otherwise poignant episode is a result of Phoebe and Cole being possesed by ghosts who run about town commiting crimes to aid them getting married as Piper and Daryll chase after them .
Also funny, is Leo's attempt at insults, which in reality are not so much insulting as they are embarrasing. Grown men should not be reduced to using what pretty much boils down to "you smell," as a derrogatory term.
I feel that this episode was a reminder that Charmed isn't always about demons but that it can also be very family orientated which is why I feel it is one of this season's finest installments.