Star Trek: 10 Things You Didn't Know About Rom
3. Mirror For Mirror
If you really want to get the measure of the mirror universe, and leave a lasting impression, send the Ferengi! For Deep Space Nine's final outing into the alternate in The Emperor's New Cloak, that's precisely what they did with Zek, Quark, and most importantly here, Rom.
For exec. producer, and the episode's co-writer, Ira Steven Behr, commenting in the Star Trek: Deep Space Nine Companion, The Emperor's New Cloak was first the opportunity to show that Deep Space Nine could be "serious" and "pretty silly" at the same time.
Second, through Rom — "one of his favourite Ferengi" — it was Behr's chance, in his words, "to question the whole lunatic idea of the mirror universe". Indeed, after a lot of confused questioning, Rom does ultimately conclude that "it [the mirror universe] doesn't make any sense".
The titular cloak also provided for some fine physical comedy during the episode. For the scene in which Rom and Quark must carry the Klingon cloaking device down the Station's corridors, Max Grodénchik and Armin Shimerman reportedly "practised for three days, carrying something that wasn't there".
In the end, on set, the actors were given transparent filament connected to four dowels to assist their performance. The scene didn't quite work as expected, however, so producer René Echevarria came up with the idea to "make it [the cloaking device] fritz". Just don't touch those induction coils!