Where it comes from
Seth says in Ep. 7 that he calls the early-2000s SNL stretch 'a golden era'.
Why fans love it
The tiny article 'a' is a humble-brag with a built-in dodge: it is self-congratulation that politely avoids insulting other eras. The machine transcript turning it into 'Nan Golden' adds a dumb accidental pun.
Written by the AI from the transcripts. Every sentence was checked against them, one by one (the full episode transcript wherever a sentence names one); 6 sentences that failed the check are left out. How the check works.