Although it's Played for Laughs, the opening is a sobering look into how the world has become so addicted to the OASIS that they neglect what's around them.
We see a look at Wade's home life, where he's abused by his stressed Aunt Alice, and bullied by her boyfriend. When he's alone, sitting helplessly on the floor like a pitiful child, we hear a voiceover of him soberly narrate to the audience about how his parents died.
The entirety of the scene also counts as a look at how socially inept he is in the real world. In the OASIS, he's the confident, brave Parzival. But when it comes to facing his real-life problems, Wade Watts is but a timid, powerless boy with just barely enough self-esteem to stand up for himself.
Wade trying to warn his Aunt Alice that their home is about to be blown up, only for her boyfriend Rick to intervene the call and ruin Wade's last chance to reconcile with his Aunt, and vice versa.
Halliday and Morrow's conversation in the beginning. Morrow is trying to explain that the OASIS has become such Serious Business that they need to take responsibility and set up rules, but James ain't having it. As Og presses the subject, Halliday retreats into his shell, and it is heartbreaking to see these two friends begin to fall apart.
Art3mis giving her backstory about why she's turned off by Wade's immersion in the OASIS. According to her, her father was so addicted to the OASIS that he neglected his own health and finances to the point where he ended up being an indentured servant to IOI and died an indent. And later, we see poor Sam look so frightened when IOI finds her and tells her she has to pay off her father's debts. She's reliving the nightmare of her father's indentured servitude, only now it's first-hand.
After Art3mis completes the second challenge and earns the Jade Key, she's about to talk to Anorak (Halliday's avatar) about Kira. But Anorak/Halliday interrupts her with a well-meaning "Go on". Translation: it's his way of saying "I don't want to talk about it".
Aech/Iron Giant getting momentarily trumped by Sorrento's mechagodzilla. Later, the poor guy pitifully holds on for dear life (while he makes a bridge out of himself), as I-R0k starts sniping his fingers off. Finally, we see him fall into the moat of lava and melt away.
The entire scene taking place in Halliday's bedroom after Wade passes the final test. When he's explaining things to Wade about why he created the OASIS, you get a sense of the sadness he must have had. Halliday's goodbye is also one that can cause viewers to choke up
Adding to the feels is the presence of "Kid Halliday", a recreation of James Halliday as he was when he was a child. "I-I like to keep him around." While the adult version is delivering the Anti-Escapism Aesop, Kid Halliday is just...playing his Colecovision console, heedless to what's happening around him. It really bookends the fact that this brilliant software designer is, from start to finish, just too scared to face the real world, and so threw himself into an artificial one to avoid the pain. It's only when Halliday takes his leave that Kid Halliday shuts the game off to go with him.
After Halliday bestows the Egg and is about to leave, Parzival stops him.
Parzival: Wait, Mr. Halliday, there's something I don't understand. You're not an avatar, are you? Halliday: ...No. Parzival: Is Halliday really dead? Halliday: ...Yes. Parzival: Then...what are you? Halliday: ...Goodbye, Parzival. Thanks. Thanks for playing my game.
Sorrento, just trying to talk to his boss. By then Halliday is a digital business legend, and could have easily steered Sorrento down a better path by explaining why his idea aren't good for players or the company. Instead, all he says to Sorrento when we see the flashback is, "This is really good coffee."