For example, we learned about Chief of Police Hopper's family during season one through emotional flashbacks.
We saw his daughter, Sara, having a panic attack and later dying in hospital from what appears to be cancer.
Everybody Missed This Heartbreaking Detail In Stranger Things Season 2 NETLFIX 2Netflix
When Sara is having a panic attack she is wearing a light blue hairband which at first seems unremarkable.
That is until we notice the same hairband on Hopper's wrist as he wears it as a bracelet during the hospital scene and later on in the season as well.
It's clear he dearly misses his daughter and this little detail brings a tear to the eye.
Everybody Missed This Heartbreaking Detail In Stranger Things Season 2 NETFLIX 3Netflix
Especially since jumping forward to the season two finale we see Eleven wearing the same hairband as a bracelet during the closing Snow Ball dance scene.
The tender relationship between Hopper and Eleven is one of the best things about the second season as we see the police chief change his ways as he takes the young girl under his wing.
He ends up adopting her as his own daughter as he is given a birth certificate for 'Jane Hopper'.
It is no surprise then that he passed on this memory of Sara to Eleven, a really sweet touch.
Everybody Missed This Heartbreaking Detail In Stranger Things Season 2 NETFLIX 4Netflix
Something else you may have missed on a first watch is Sean Astin's Bob making reference to Pennywise the Dancing Clown from Stephen King's hit horror novel It.
In an early episode of season two, Bob attempts to help Will deal with his nightmares even though at this point he has no knowledge of the Upside Down.
Bob tells Will about a recurring nightmare he had as a child about a clown he had met called Mr. Baldo.
Everybody Missed This Heartbreaking Detail In Stranger Things Season 2 it pennywise clown movie 1048x694Warner Bros. Pictures
In his nightmares the clown would continually offer Bob a balloon and it wasn't until he stood his ground and told Mr. Baldo that he wasn't afraid did the nightmares stop.
If you have read It or seen the film adaptation that made waves earlier this year, then this will sound familiar to you.
Plus, Bob is from Maine which is where It is set and he would have been a child in the 1950s which lines up with Pennywise's cycle of appearances which take place every 27 years.
Everybody Missed This Heartbreaking Detail In Stranger Things Season 2 BOBNetflix
This could mean that Stranger Things and It are set in the same universe and would also make sense of a mysterious tweet Netflix shared in the lead-up to the second season.
An innocuous image of a plain white background with a small tear in the corner, which looked like it had been torn by a pair of hands, Netflix had us all hooked with this simple and sinister post.
[ame]https://twitter.com/Stranger_Things/status/923549792994713600[/ame]
Although many were left confused, if you're familiar with the original television adaptation of It, the image may mean something to you.
That is because it is remarkably like the DVD cover for the miniseries:
Everybody Missed This Heartbreaking Detail In Stranger Things Season 2 WarenerWarner Bros. Television
The cover comprises of a white background with Tim Curry’s terrifying clown Pennywise creeping into the top right hand corner as his hands tear away at it.
The only difference being Pennywise is nowhere in sight in the Netflix tweet, although his hands appear to have been all over it.
But let's not dwell on Pennywise's creepy connection to Stranger Things - let's remember the second season for the absolute sweetheart that is Police Chief Jim Hopper.