[DISCUSSION] Loose threads: The Earth duplicate planet from TOS episode Miri
Season 1 episode 8 (IMDB), episode 9 (Paramount), or episode 11 (Memory Alpha). Anyway, we get a complete copy of Earth, the failed longevity experiment, bonk bonk, and Kirk wrenching a kid off a desktop. Beyond that, no explanation surrounding AN EXACT COPY OF EARTH! Zero, zip, zilch, nada.
Side query: What's considered the "official" episode breakdown?