How a large portion of the cast end up in the present:
Aniq, the AdorkableNice Guy, was arrested at the insistence of Xavier when they were in high school. Fifteen years later, he's an escape room designer who's going through a financially difficult time and is still getting screwed over by Xavier, who interferes as Aniq and Zoe finally reconnect after several years apart. The afterparty isn't much better as he's suspect number one and would've likely been arrested if it weren't for Danner.
Chelsea was the class president of 2006 and showed a great promise for her future. Unfortunately, it all came crashing down at Walt's St. Patrick's Day party, when Xavier almost date-raped her and then spread the rumor that he, her, and Walt had gotten into a threesome. That incident destroyed her reputation amongst her peers and ruined her chances of a well-off career. In the present, she's a vet's receptionist, has been dumped by her ex-girlfriend, and is regularly derided by her former classmates, especially for "ruining a happy family" by having an affair with Brett, which he shirks responsibility for. By the time you learn all of her backstory, you just want to give her a hug.
Yasper tries to be upbeat and energetic in public, but in reality, he's a deeply desperate individual who wants nothing more than the fame he thinks he deserves. His big musical numbers actually become quite depressing in hindsight, especially Yeah Sure, Whatever, after you learn that a lot of it was in fact him plotting to murder Xavier for brushing him off as an afterthought. Even after committing the act, he tries hard to help Aniq "solve" the case as he doesn't want his dear friend to be arrested, a point which he emphasizes after getting caught.
Zoe moved directly from graduation to working for her old high school, becoming vice principal because it was what she felt like she was "meant to do," instead of what she wanted to do. She also ended up repressing a lot of her fun side for the sake of her career and family, resulting in what is represented as various different versions of her fighting for control of the 'real' Zoe. She also becomes genuinely distraught when she thinks that Brett is responsible for Xavier's murder.
Not much is known about Walt in the present. Because, he's so brushed aside by his former classmates that no one cares to learn about him. He literally thought the best way to get their attention was to streak, which goes to show how messed up the poor guy is by years of neglect.
Along with Chelsea's reputation-destroying humiliation, two other moments stand out from the fateful St. Patrick's Day party:
Yasper breaking up Ska-pe Diem stands out as the only moment in the series where Xavier is portrayed as being completely sympathetic. He, an insecure and awkward teen who is derided by most of his peers as a loser, is suddenly rejected by his bandmate and seemingly Only Friend explicitly because he finds him to be too embarrassing to associate with. While Yasper tries to be tactful about it and Xavier quickly squanders whatever pity the audience has for him afterwards, there's no denying that this was a gut-punch to someone who was already having a hard time. The sequence even gets a unique song that plays as it happens, which is fittingly the most depressing track in the season.
Aniq destroying Xavier's car, their ensuing fight, and his arrest. While the fight itself is Played for Laughs, it's still heartbreaking to see bad feelings get so intense that Aniq, a kind and reasonable Lovable Nerd, is pushed to irrational violence and Xavier, projecting his frustrations onto Aniq, decides to press charges against him with the aim of ruining his life. In particular, the camera cuts to Yasper several times throughout their fight and clearly shows him to be upset and confused by his two friends suddenly attacking each other.
Danner's past is shown in the seventh episode and turns out to be surprisingly harrowing. She joined the academy with the hope to do good, but in fact, accidentally got a young teenager, Willow, caught up in a murder case. When she tried to set things right and provide evidence that exonerated Willow, Detective Germain purposefully got her demoted and remained antagonistic towards her until she got a transfer to another department.
Yeah Sure, Whatever becomes very depressing in hindsight after you learn of Yasper's motive and how the night really went. However, his fabrication of the event can almost be seen as him trying to construct a fantasy world to live in where Xavier was accepting of his request.
Hell, even Brett earns some sympathy, despite being an arrogant, insensitive prick for a good portion of his life. In the finale, it's clear that the series won't end with him as the killer in a half-baked reveal, but Ike Barinholtz's panicked performance almost fools you into thinking that Brett will be put away for a crime he didn't commit.
Aniq and Zoe’s reaction to when Danner’s theory that Yasper killed Xavier is proven right. Instead of celebrating like everyone else, they hang their heads in solemn acknowledgement and express a realistic level of grief at the fact that one of their friends could commit such an act.
Season Two:
The corpse of Edgar is discovered by his newlywed wife, Grace. And then she ends up being the prime suspect.
The night before wasn't much better, as Edgar left Grace in the middle of the first dance during their wedding and later has a seemingly drunken outburst. After he passes out, Grace simply lies down in her wedding dress and cries.
While Aniq and Zoe are doing well in their relationship, Aniq tries desperately to impress Zoe's parents at the wedding. It only results in Feng's new snow cone truck getting dented, Vivian getting covered in spit-up camel's milk, and Aniq accidentally leaving their relatives at a motel while picking up a group of strangers. By the end of the night, Vivian reveals to Aniq that he's been acting exactly like Brett, caring what they think while all they want is for him to care about Zoe. The look on Aniq's face when he realizes how he acted is heartbreaking.
Travis, although largely an overconfident conspiracy theorist, believed that Edgar was out to hurt Grace and was trying to protect her out of the goodness of his own heart, not to win back her affections. The end of his episode can tug on the heartstrings as he makes his case to Danner and Aniq.
And the reason he suspects Edgar? Because Edgar is in crypto, and Travis was scammed due to a phony crypto scheme. Sure, there's the implication he's acting out because of his own misfortune, but it's hard not to feel at least a little bad for the guy.
Feng's testimony is sad from start to finish. Throughout the weekend Feng tried to be present and thinking about his daughter's wedding but could not stop himself from prioritizing trying to save his failing Bao Bing business. Over the course of the night he had to desperately try to hide his financial troubles from his family including that his catering truck had been repossessed during the wedding, as he desperately tried to secure investment from Edgar. Because this episode is told through his employees' social media videos rather than his own account, we get to see Feng realize just how much he was prioritizing the business over his daughter and how much he humiliated himself. After Aniq tells him that he should let his family know about his money problems before they come to light through the videos he admits on the verge of tears that he cares less about the money and more about not failing at something that he did to show his wife he could be adventurous.
