The one where Dean and Cas finally get to live an apple pie life where they fall into routine and their biggest problem is if their beloved Petunias get enough sunlight

“Hey Cas, come take a look at this”
“What is it?”
“Do you think we should cut down that tree by the sidewalk? I just think my lovely Petunias need—”
“Dean, it’s fine. Just leave it”
“But I want to make sure that—”
“Dean. We just spent all of yesterday making sure that our—”
“Yeah okay, fine. I’ll go make us breakfast”
“I’ll make orange juice”
“Hey Cas hold on, do you ever get the feeling that we’re forgetting something? That we’re supposed to be somewhere else?”
“I’m supposed to go to the market to get oranges.. and honey”
“Don’t be a smartass. You know I didn’t mean it that way”
“Dean, all I know is that I’m where I want to be”
“Yeah, me too”

They had locked something away, something deep inside them. The truth that they’d always known but chose to forget. Limbo became their reality.