In S1E18, Emily comments that Rory and Lorelai are being very quiet at dinner. They reply that they’ve just been busy with school, work, life. Lorelai follows up with, “Dig it, man.” Rory replies, “Peace out, Humphrey.”
This is a weird reference, and it’s probably mostly nonsense but I think Rory is technically referring to Hubert H. Humphrey, 38th Vice President of the United States (as opposed to Humphrey Bogart, the actor who died in 1957). Hubert H. Humphrey was Vice President under Lyndon Johnson from 1965 to 1969, and he was a senator representing Minnesota before and after that. He was a pioneer for desegregation within the government and wrote the Civil Rights Act of 1964. He also introduced the first legislation proposing the creation of the Peace Corps.