Board Thread:Wiki-Related Discussion/@comment-15736398-20141111181225/@comment-15736398-20141118193908

It's not an 'either/or' thing; it's merely a matter of noting that "Smash the Mirror" is TWO episodes (labeled accordingly as 4x08 and 4x09) which were shot and aired as one, thereby explaining why there was only one Production Code assigned to them.