This song plays as Lorelai wakes up happy, gets coffee, goes outside, and falls through the porch. It was written by Jay Livingston and Ray Evans, published in 1955. It was introduced in the 1956 Alfred Hitchcock film, The Man Who Knew Too Much, sung by Doris Day. Her rendition went to #2 in the US and #1 in the UK, and the film received the Academy Award for Best Song. It became Doris Day’s signature song, and is regarded as one of the best songs in cinema history.
The song popularised the phrase que sera sera to indicate a sort of cheery fatalism, although the phrase itself was used as a heraldic motto as early as the 16th century. It is an English mistranslation of “what will be, will be” from the Spanish; in Spanish it would be lo que será, será. No such similar phrase is known of in Spanish or Italian, it has always been an English saying.
In The Man Who Knew Too Much, Doris Day sings the song in the hopes that her kidnapped son will hear it. The song’s message of hope is often used in film and television juxtaposed against disastrous events to create a moment of black comedy, of which we see a very mild version in Gilmore Girls. The joke is that Lorelai has no idea what is coming.
(It might seem unusual to go out on your porch in the your pyjamas early in the morning in the depths of winter to drink your coffee, but Lorelai has that special relationship with snow. And they’re actually in California).