Forshadowing
It always kinds of creeps me out when I watch certain episodes and there's some serious foreshadowing in them. For example when Puck and Lauren are planning on making a tape of themselves and then Holly Holiday tells them that they could be arrested for child 🌽, which Puck then reiterates at the end of the episode. Always sketches me out because that's exactly what he was arrested for in real life.
And then when Finn finds out what really happened to his father, talking about how he had a drug problem and he died from an overdose... We all know what happened there.
And of course Naya singing If I Die Young, sink me in the river during the Quarterback episode.