this is a story where the rule 63 characters exist alongside the canon ones. It's just a short comedy thing. the R63 six are hanging when suddenly Princess Twilight appears and abducts Dusk saying something about reforming him.

After Sunset and Starlight she's having a bit of a breakdown and is checking out ponies with names that could be variations of hers as potential threats

If you find the story I would also like to read that never heard of it before