“We wouldn’t miss it for the world.” For jazzypizzaz.
What I love about this parallel is that both Kurt and Rachel use the exact same inflection and phrasing. (That’s why Kurt’s line in 4.21 reminded me so much of Rachel’s, that I initially thought it was Kurt saying this in 4.06 too - thank you, jazzypizzaz, for remembering where else did I hear this sentence this season.)
And if you think about it, in the scene backstage Rachel basically answered *for* Kurt, since the question was directed at him. And in that horribly *horribly* awkward scene backstage with Finn and Rachel, that ‘No.’ was the only time Kurt said anything to Blaine (or looked at him).
Now compare this with the scene from 4.21. Kurt is answering the same question: coming to see Blaine perform. But he is so much happier about it. His body language is open, he holds eye-contact with Blaine (he was staring at Blaine that whole conversation, while in 4.06 he was unable to make eye-contact for longer than a millisecond , his smile is ~real~, not strained at all.
There was a lot of parallel between these two episodes, you can see them floating around in gifsets (like this one) and I love that we (and they) can replace those memories with happier ones.