Season 9 had some of my least favourites (e.g. The Butter Shave, The Merv Griffin Show, The Betrayal) but also some of my all-time favourites (Festivus! Kramer opts out of getting mail! Elaine plagiarizes Ziggy!)
It’s kind of a weird inside theater joke. It’s inspired by the Harold Pinter play…“Betrayal”
Wikipedia link%20move%20forward%20chronologically.)
Pinter is the name of the groom in the episode IIRC.
Thanks. I wasn’t aware of the connection to the Pinter play.
Those, and “The Andrea Doria” (which I think was in Season 8) were probably examples of Jerry Seinfeld’s wackiness untempered by the absent Larry David. I rather enjoyed them anyway; they just required the same suspension of disbelief as when watching Bugs Bunny cartoons! 
Another wacky one (don’t remember the episode, but it was Season 9) was when Kramer installs a discarded screen door on his apartment door, then sets out a patio chair, wind chimes, and something that looks like a bird feeder outside his apartment! 
I wasn’t, either. I guess that was clever, but for me that still doesn’t make the episode funny.
“The Chinese Restaurant” from Season 2 is something of a riff on Waiting for Godot and/or No Exit.
It’s fun guessing the vintage of an episode that comes on after the news, just based on Jerry’s mac. He even had a short-lived Duo, where you could pull out the center and that’d function as a laptop.
So did Alfred (in Batman & Robin, it was dramatically lit and looked gorgeous).
Well, I’m done the binge-watch of the whole series, except for a couple of the early episodes that I skipped that I guess I’ll now go back to.
I was mistaken in saying earlier that some half-remembered song about “time of our lives” was in the finale, and it was the wrong song,anyway. But there’s a part of “The Clip Show” preceding the finale where highlights of the clips and bloopers from the previous nine years are played to a tune that includes the lyrics:
For what it’s worth it was worth all the while
It’s something unpredictable but in the end is right
I hope you had the time of your life.
It was a great team of cast and writers and a historical contribution to television entertainment. Now that I’m done, except for a few old episodes, I haz the sad. 
ETA: They absolutely should have ended the series with “The Clip Show”, a nostalgic review of the previous nine years, including funny outtakes. Despite the genius of the series overall, I have to say that the finale was really disappointing and should never have been done.
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That song is “Good Riddance” by Green Day.