According to his 50 Facts video, he has four siblings that died as miscarriages, and he himself almost died from an allergic reaction at a young age. He was also bullied in school, and the bully died before finishing high school.
And according to this video, Chugga almost got on the Thunder Mountain roller coaster that derailed in Disneyland, killing a person and injuring 10 other people. He's had a fear of roller coasters ever since.
Especially keep in mind how he was planning on riding in the front, which was where the person died. He was one ride away from likely dying.
His reason for naming his Jolteon Voltaire, after a friend from when he was a teenager.
Chugga’s story about what happened to a friend of his while they were climbing on Mt. Coronet. Basically, the friend encountered a Shiny Graveler which used Self-Destruct on the first turn. And his next encounter is another Shiny Graveler which did the same thing. Although this is a very funny moment since it’s “the best-worst luck”, imagine if that is the only time the friend could encounter a Shiny Pokémon in his life, and just like that it’s gone before he could do anything. On top of that, losing the chance to capture a Shiny Pokémon with something like that happening is one of the most devastating moments that could happen to anyone.
Chugga mentions in one Fortune Street video that his mom worked at a hospital and got a really nice pen from some company. When he was 12, he took said pen to school. The pen had the logo of a drug company and he was forced to throw it out, making his mom really upset since "she loved that pen". Ouch.
And remember those hilarious moments in his Sunshine LP? Like the trouble he had with the watermelons, or the really annoying level that he completed right before losing his save data from a power failure, or the huge annoyance the final level's blue coins were? Not so funny when you consider he was the one playing during that, in addition to the problems he was already having. Somewhat surprising he didn't have a Heroic B.S.O.D. by the time it was over.
Chugga has links to the alternate scenes in Majora's Mask that play when you fail something. Throughout the alternate scenes, he's completely silent, and the description of the video is almost never more than the affected person/thing's name, followed by an ellipsis.
In Super Paper Mario, during the scene where Luvbi turns into a Pure Heart, which is already enough of a Tear Jerker, Chugga stays completely silent, not even reading the text out loud. Then, once the scene ends and he gets the Pure Heart, he doesn't even yell "YOU GOT A PURE HEART! END OF CHAPTER!" like he always does. He just stays silent, quietly reads the text at the very end, and then ends the video there without even any closing words.
The other Wham Episode, Chapter 18. It ends with the sad part of the flight music from that chapter. A translucent image of Palutena is slowly fading in, and she repeats her (or rather, the Chaos Kin's) quote, “Everyone changes, Pit. Even gods.”
Any time Chugga finishes a playthrough could qualify, particularly if it was one of your favorites or if the ending was sad (MOTHER 3, Super Paper Mario, Ōkamiden). The way he talks about how much fun he had with the playthrough...
In the finale of The Legend of Zelda: Link's Awakening, he talks about how meaningful the game, especially the ending, is to him, as someone who suffers from nightmares rather often. After that, he viewed the ending for the first time and it made him love the game even more.
At one point while making Xenoblade, Chugga became ill, and his sickness got worse and worse for over a month and a half. After 45 days of no updates, he made a video explaining it. He didn't know when he'd feel better, and until then, he could't make videos at all. It's utterly depressing, not just for his viewers who were looking forward to watching Xenoblade, but for Chugga himself, who felt as though he had no energy...and considering how energetic he usually is, that's honestly heartbreaking.
Especially if you listen to how tired he sounds, when compared to how much energy his voice usually has.
Staying with the tradition of staying silent after major events, Chugga is completely silent after Fiora's death in Xenoblade, even after a new mechanic that he would normally explain is introduced involving the Face Mechon. The ending shot is also Fiora fading out to represent their death.
His entire absence between the Metal Face battle and the aftermath of said battle. Many people spent countless hours watching his old vids and wishing him to come back. When he returned a few days ago, he spent the middle part of Xenoblade episode 41 talking about how he found the strength to come back. The real tearjerker is when he acknowledges the two people who helped him return to Let's Playing: fellow The Runaway Guys member ProtonJon and Masae Anela.
On November 11 2014, Chuggaa posted that he was sick again. To be more specific, digestion problems that arose due to the medication he was taking during his previous infection.
Emile had begun to post various things about the first aftermath episode of Xenoblade on his Twitter, and then he reported his computer crashed, and it's gonna be a while. To think... all that progress went down the drain due to some stupid luck.
During Platinum, he encounters a trainer who said he brought his Pokémon to work. Emile then tells a story that he brought a Pokémon game to work once and played it on his break, his boss saw him, asked what he was doing and upon seeing Emile had over 100 hours clocked into a Pokémon game, his boss said Emile "had no life and was such a tool."
On February 1, 2016, Chugga announced that his cat Teddy had passed away. Even more, it left him silent for the past several days before the announcement.
That's not even half of it. When he made the announcement on Twitter, Chugga referred to Teddy as "our cat and good friend," fully aware of how much Teddy had grown on his fans, almost like they were one big family alongside the duo.
It got heart-shattering when he recaught Teddy, his Slaking. Particularly with the "Teddy, come back!" part.
Near the end of the final episode of Platinum, Chugga reveals he was ridiculed and beaten up in high school because he enjoyed Pokémon before Diamond and Pearl was released.
Revealing in this episode of his playthrough of Mario & Luigi: Partners in Time that in his childhood, when his family wasn't financially strong, he was given a wallet for his own money...because his parents wanted to know where his money was when they were in a pinch, with Emile not catching on and his parents feeling terrible for having to take their child's allowance.