Curate, connect, and discover
Thinking about s2 ep3 where Jeff has his whole freak out over cholesterol and Duncan is the one to come up after class to him and check up on him.
"Mind if I ask what happened in class today?"
It's so simple but Duncan clearly noticed something was wrong and it shows how their friendship is genuine. I seriously wish we saw more of it because while horny loser Duncan is hilarious, he also deeply cares about his friends and can give genuinely good advice.
"While claiming to have no religion, you were actually devoutly worshipping yourself. And now that your God has high cholesterol, you're trying to kick Pierce's in the balls."
And it's so rare to see people worry about Jeff because he always convinces people that he's got it, so people brush it off. But Duncan has been a stable support for Jeff since the pilot when he cared enough to teach Jeff a lesson.
He sees through Jeff's bullshit but he also deeply respects him.