One of the most epic episodes, of course. 

Watching it the first time I knew that Twilight would bust in making wild accusations with no proof. And "Cadence" would cry to get out of it. 

But Chrysalis's transformation took me totally off guard and I really loved her design. I heard it actually scared some kids. I like when kids shows don't play it safe.

And I really want to see what kind of an epic bachelor party Spike would throw! There must be a good fan fiction about that somewhere.