A-Plot (GN59): Gender wage gap, Family Versus Career, workplace sexual harassment
B-Plot (Harry's radio): Women being ignored, objectification, workplace sexual harassment
C-Plot (Max and Sahar): Beauty standards
Ass Pull: In season 2, Harry reveals the ability to erase people's memories and create false ones which would have been very useful in the previous season. Handwaved in that the biggest thing that he would have wanted to hide - revealing his true nature to Asta and Dan - he excuses as not being alone anymore.
Catharsis Factor: Throughout the first 2 seasons of the show, Deputy Liv makes comments about her grandmother, Nana, who apparently hates her just because Liv stole her deviled egg recipe when she was a kid. Then in the third season, Nana makes her first on-screen appearance, and she’s just as horrible as Liv stated, yet Liv isn’t able to stand up to her. It gets worse when we find out that Nana has been actively using Liv’s fascination with extraterrestrials to discredit her granddaughter, giving a scathing interview to the local paper and leaving “anonymous” suggestions at City Hall claiming Liv isn’t fit for duty. As such, it is IMMENSLY satisfying when Liv, backed by Mike, goes to confront her grandmother about her abusive and manipulative nature. While she has a weak start, more sniping from Nana causes Liv to lose it, ranting at her grandmother, which ends with a 10-second-long cursing, resulting in Nana being so shocked that she has a (non-fatal) heart attack. The cherry on top? As Nana is being taken away by paramedics, Mike helps Liv steal ALL of her grandmother’s recipes.
The Firefly Effect: Given that the series stars a Firefly alum as its lead and received glowing reviews, many people posted that they didn't want to watch it because they figured it would just be canceled. This sentiment was so strong that some people were still posting this even after the news of the show's renewal.
Just Here for Godzilla: A lot of people tuned in just to see Alan Tudyk flex both his comedic and dramatic muscles in a leading role for once.
The effects of Harry's device on a random hiker. He's suspended in the air, unharmed but unable to move. His rotten corpse is found, still floating in the same place, alongside a couple of birds. It's implied he was stuck there for so long he just starved to death.
In a minor way, the effects of the device in Harry's dream, which is presumably based on the actual effects. It's shown that people are disintegrated but animals are unharmed. That would leave hundreds of thousands of animals trapped in homes, zoos and other buildings they'd have no hope of escaping.
Aliens are real and have been on Earth for years, some of them doing stuff like kidnapping children for purposes of anal probing. Another was planning to kill all humans and there's another group of aliens planning to take the Earth over. Very few people have any idea of any of this.
The Greys are doing more than just anal probing, they're kidnapping children before they're even born for the purposes of creating human/Grey hybrids and are planning to eventually desolate the Earth entirely.
Rescued from the Scrappy Heap: Sheriff Mike Thompson was generally disliked by a large portion of the fandom for his abrasive behavior in general and his awful treatment of Deputy Liv Baker. He is now generally a lot more liked for the genuine chemistry between him and Liv now that they've made up, and it being revealed that a large part of his behavior was due to unresolved grief about the death of his partner and childhood friend.
The Scrappy: For some, Kate Hawthorne will Never Live It Down for falling for Harry's lie that Max is mentally ill due to his apparent paranoid delusions.
