Throughout the run of Superstore, the workforce of Cloud 9 Store 1217 did a lot of insane and horrifying things. It wasn't It's Always Sunny in Philadelphia levels of horrifying, of course, but still ridiculous in their own way. But in all of the absurdity that happened on Superstore, possibly the worst crime in an individual episode was the one Cheyenne and Glenn committed against all of geekdom.
By the time Season 4, Episode 20 rolled around, a few things had changed in Store 1217. Glenn demoted himself back down to being a floor worker so he could spend more time with his family. And Amy, who had recently had her second child, was promoted to Manager after blackmailing her District Manager. It sounds like she did something awful but it was the right call given the circumstances.
But the staff were really starting to feel the financial crunch. Working retail is rarely a profitable experience for anyone doing the day-to-day grind on the sales floor. Things were getting even worse as Cloud 9 corporate was pushing Amy to get by on fewer and fewer hours for her staff. She kept having to rework the schedule to try and alleviate the pain as much as possible. This usually meant just taking Jonah's hours and giving them to everyone else.
In the meantime, Cheyenne and Mateo came up with a plan of their own. They figured out a way to sell their old stuff in the store using its existing point of sale system and having the money sent to another account. It worked well enough that Glenn wanted in on the action. As such, he brought in a box of stuff from his house that included a Mickey Mantle rookie card and a copy of Action Comics #1. There is no greater artifact in all of geekdom.
That's when Cheyenne and Glenn committed an absolute atrocity. Not knowing the value of the artifacts in front of them, they threw the old baseball cards out. This was rectified later in the episode when someone from corporate who was visiting the store rescued Mickey from the garbage. At the very least, this piece of history was saved from utter destruction, even if Glenn didn't make any money from it.
The copy of Action Comics #1 did not fare as well. Glenn was about to throw it out, too, when Cheyenne grabbed it, ripped a chunk off the cover, and put her chewed-up gum in it. Witnessing the utter destruction of one of the most valuable comics ever printed, even in jest, is too much for a self-respecting geek of any variety to bear. The only thing arguably worse would be the destruction of a 25-year-old, unopened copy of Super Mario 64.
Similar jokes where priceless artifacts are destroyed have been done before. And Action Comics #1 is a popular target. But this moment in particular was especially rough because Glenn needed the money pretty badly. Selling either of those items could have solved all of his financial problems. That being said, not demoting himself would have prevented Glenn from giving up the $90,000 per year he lost and avoided those problems in the first place.