Sister: Josh, are you okay?
Josh: I want to text Laura, but I don't know what to say.
Sister: You said it was an emergency.
Josh: Well, it is. I pretty like this girl, I don't want to blow it.
Sister: Oh, my God. I got it. Okay. "Laura." Period. "It's your stranger from the train."
Josh: (Gasps) Film reference.
Part of the transcript from Season 1 Episode 2 of Man Seeking Woman
The guy (Josh) is asking his sister to make a sentence for a girl he likes. She made a sentence and he was impressed by it saying Film reference. It seems like awesome. What's this meaning?