I disagree a bit with the sibling commenter. This episode falls into about the second season of the show midway through. So putting yourself into that context: you’re watching something like 35 episodes of this show and it’s cute and wholesome and the stories are great, some with some emotional impact, but then you get to this episode and it just absolutely blindsides you.
So, I think it will _make sense_ on its own, but I think it _really_ hits hard if 1) you weren’t expecting it and 2) if you have kids.
The blindside being the unique tone of the episode, compared to what came before it. It still has silliness and is a fun watch.
Some things that I think make it hit differently:
* The house and most scenes are dimly lit
* You see the family in various stages of sleep
* The musical score has some intense crescendo
* The vulnerability it shows
It's a small glimpse of night time in a house with a child that is still transitioning to sleeping on their own. Having had kids, that weight being lifted as they finally "get it" is a unique feeling of bittersweet relief. It also shows the lengths the parents go through to make it a graceful and comforting transition.
This is how I felt about the episode before I had kids. I thought it was a fine episode but nothing special. Onesies was my favorite. Of course, we wanted kids, so that hit me where I was at the time. Now I have a two-year-old, and I "get" Sleepytime. There is nothing extra to explain except that it will just mean more to you.
Not saying you don't have kids, just my own experience with it.
So, I think it will _make sense_ on its own, but I think it _really_ hits hard if 1) you weren’t expecting it and 2) if you have kids.