And I mean nerd in the most endearing way possible. Young Randall has been shown to be very good at math, love Rube Goldberg machines, and keep notes on how to get along with brother Kevin (aww). Young and adult Randall have also have also been shown to have anxiety, which adds a significant emotional layer to that viewers don't often see in stereotypical smart or "nerdy" characters.

We also know that Randall will grow up to be a successful adult, a loving husband, and a great dad, which totally subverts the old-fashioned thinking that nerds can't be cool — he even calls himself Randall "Cool" Pearson.

Randall and Kevin haven't always got along — as kids and as adults. Kevin has said that he resented the "special" treatment Randall got from their parents, while Randall admitted that all he wanted was some kind of affection from Kevin. As adults, though, it seems like the siblings are finally in a good place, but it's still emotional to see flashbacks in which the young versions of the characters don't quite have their dynamic figured out yet.

With all this talk about Jack and the mysterious house fire, I personally forgot that Randall quit his job last season. In Season 2, viewers have gotten no indication that Randall is headed back to the corporate world after his existential crisis in Season 1. Instead, Randall is embracing life as a stay-at-home dad — and Beth is the family breadwinner, which is still rarely seen on television.

Here's another This Is Us puzzling mystery to solve: Why does Kate resent Rebecca so much? Kate has implied it is due to Rebecca being "beautiful," but the real reason is likely to be something much deeper than that. Is it because they have both pursued singing? Where did their mother-daughter bond start to falter? Sure, answers to those questions would be great, but this plotline also reflects not every mother-daughter relationship is like Gilmore Girls.

"The Kardashians are like gremlins. By next week, there will be a bazillion more of 'em," Kevin said in an episode that aired in the same week filled with Kardashian baby rumors. OK, Kevin and the This Is Us writers don't necessarily need to be psychic to predict that, but if you're only focused on Jack and the fire, you might miss more prophetic Kevin jokes.

Before fans obsessed over the hows and whys of Jack's death, the mystery of how Miguel and Rebecca fell in love was a main point of concern. Of course, now with the fire obsession, questions about Rebecca and Miguel's own love story have been pushed aside, when they shouldn't be. Just how did this happen? Did Miguel comfort Rebecca after Jack's death? How did the Big Three handle it? Fans need to know this, too.

Kevin and Kate have always had a solid connection and understanding with each other, which Kevin has called their "twin" thing. Technically, Kevin and Kate were born twins — and just like twins, they are very close. It was even revealed that Kate was the sibling who had to relay the news of Jack's death to Kevin. It's also a close brother-sister bond that Toby has had difficulty understanding and it may continue to be an issue as Kate and Toby raise their own family.

This Is Us has multiple actors who play the Big Three at different stages of their lives — and the young ones resemble their adult counterparts in so many ways. It's almost eerie, but the casting truly makes you forget that you're not actually watching different actors.

There are plenty of clues and theories about Jack's death to comb through, but you should definitely take a break once in awhile to appreciate the amazing other characters and mysteries on This Is Us.