PUZZLE #18: Play Again (and last week's meta results)

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Hello, solvers!

Last week's meta was a layered one. 31 solvers sent in the correct answer-- but how did they do it? Let's find out!

In this "Stranger Things"-themed puzzle, solvers were prompted with "Researchers of this grid have discovered the existence of an alternate dimension, which some have called the Upside Down. The scientific world is abuzz-- but there's rumors that they also discovered something else in the puzzle. What did they find?" In doing the crossword itself,  two things became clear:

1. The bottom half of the grid is a mirror reflection of the upper half. More tellingly, though, the down answers in the bottom half of the grid had to be flipped (indicating that this is the Upside Down), as were the clues for that section of the grid (at least in the pdf).
2. Two answers (COME THROUGH and ONLY CONNECT) had starred clues.

So, where to go from there? Nudged by the two starred answers, solvers noticed that the "normal" side and the "upside down" could be connected. When certain letters are added between the two halves, words are created in the Down direction that work equally well for the given clues. More specifically:
[Common means of getting to work] could clue CAR or CARPOOL
[Operating smoothly, say] could clue WELL or WELL-OILED
[Place to crash] could clue BED or BEDROOM
[Place to grab lunch] could clue CAFE or CAFETERIA
[Beat a retreat] could clue RUN or RUN AWAY
[Chap] could clue GENT or GENTLEMAN

The added letters, as shown above, reveal the PORTAL that connects our dimension and the Upside Down (and, incidentally the meta answer). It was a big part of season one, but I've only seen two episodes of the latest season. So, I don't know how relevant it still is, but whatever. Also, I'd like to extend a thanks to all the entrants this week, for not spoiling the new season. What a courteous bunch you all are. Of those entrants, this week’s winner is... Nathaniel Lee! Congratulations, Nathaniel, and thanks to everyone who sent in comments. They’re very much appreciated.

Smaller puzzle today; I've been busy at school, so here's a lil' grid with a lil' theme. I really like it though, and I hope you do too.

-Paolo