One moment in particular that slipped under the radar Tuesday occurred during one of the flashback scenes set in Vietnam. After a young boy comes up to Jack (Milo Ventimiglia) to give him a fresh fish, the boy's mother runs up to scold him.
The woman appears on-screen for just about five seconds, but it was enough time for eagle-eyed This Is Us fans to notice something peculiar about her outfit.
On Twitter, several viewers pointed out that the woman is wearing a necklace that resembles the one Jack gave Kevin (Justin Hartley) as a present when he was a teen.
In Season 2, Jack gave Kevin the necklace after he was injured in his high school football game. Since then, the memento was very important to Kevin, and it was the one item Jack saved for Kevin in the family's house fire.
The scene in which the young boy interrupts Jack's conversation with his superior does seem a bit random, and, as we know, the This Is Us writers don't add any characters in by accident.
Reddit user also thinks the woman's cameo could signify that she and Jack will somehow be involved in a relationship. "[Writers] made a point of showing her and Jack defended her when the other soldier was saying her little boy would try to kill them when he turned 15," the user says.
Only time will tell if any of these fan-theories are true.