An awful lot happens in this episode: Phoebe is preparing for her wedding; The Seer is conspiring to be the mother of Phoebe's unborn child; Cole is scheming to sabotage the wedding so he can lure Phoebe into a dark ceremony; and Paige's growing suspicions of her soon to be brother-in-law escalate further with some fantastic results.
This being Charmed, there are a few candyfloss sub-plots thrown in to appease the younger audience. These slap-stick elements are far from the worst comedy attempts from this series, but we certainly could have done without them (although Cole as Piper was a highlight, and that in part is due to an eerily laconic Piper hexing Paige and Phoebe).
Again, the crux of the episode's success lies heavily on the Source's attempts to prevent the marriage from going ahead, and Paige's persistence in communicating to her sisters that there's something not quite right with Cole. Rose McGowan is in top form here – she looks absolutely stunning throughout, and she really conveys Paige's conflicting emotions laudably.
Likewise, Julian is having a blast playing the villain again. The Source's efforts may come across as contrived at times, but for the most part, it's genuinely exciting watching him be one step ahead of the sisters. And the reveal in the cemetery was a definite highlight: his blasé reaction when Coolio outs him is fantastically underplayed and a magnificent WTF moment.
All in all, 'Marry Go-Round' pushes the arc into overdrive and mostly works because of that. It's great to see Darryl and Victor again, and for once, the girls do not come out on top. In fact, it's a rare Charmed episode where everything works against them. That montage sequence at the end was bittersweet; Phoebe gets her dream wedding, yet little does she know she's been tricked into a dark wedding, blood ritual and all.