A routine send-off. The origin is from the airlines, when the flight ended, and stewardesses bade farewell to planeloads of passengers as they filed out.
Passenger 1: "Enjoyed the flight."
Stewardess: "Buh bye."
Passenger 2: "See you next trip."
Stewardess: "Buh bye."
Passenger 3: ""Bye now."
Stewardess: "Buh bye, buh bye, buh bye, buh bye...."
12 step recovery jargon referring to someone new who talks about how great life is, now that they're sober. Usually meaning that the person is out of touch with reality.
The new guy seems pretty happy for a dude who has no job, no money and no family. He must be on a pink cloud.