Greg responds...

I'm not sure what you mean by "episode number". As I once explained, each episode of the series had a production number from Walt Disney Television Animation. Each episode also had an "episode number" from Buena Vista Television. These numbers occassionally, but not always, corresponded to their airing order.

I'll assume you're referring to airing order, because I don't see why anyone would be interested in production or episode numbers.

"The Mirror" was designed to be (and actually was) our 18th episode. It was preceded by "A Lighthouse in the Sea of Time" and succeeded by "The Silver Falcon".