A bleeding and near-death Walter White (Bryan Cranston) was in a lab for the last time as "Baby Blue" from British rock band Badfinger played.
The song was a top 20 hit in 1972 from the band's album "Straight Up." It was reportedly written about Dixie Armstrong, a woman lead singer Pete Ham dated while on tour in the U.S.
The series finale provided a string of surprises, but not as big as the one for Joey Molland, the only surviving member of Badfinger.
"Baby Blue" has shot up the charts since the finale -- including a 9000 percent stream increase on Spotify. Because Ham wrote the song, Molland had no idea the song would be played in the episode.
"The song sounds great — I’ve always liked the record myself. It’s one of my favorites, for sure. It was a big hit for us, too," Molland said.
"So it was great to hear it. And I’m glad they used our version of it and not a recut of it. It’s great, you know? Today it’s in the charts, and yesterday it was kind of like an oldies record!"
“I think Pete would be knocked out to see this,” Molland said.
The song is the finale of a series full of blue-themed musical numbers, including "Crystal Blue Persuasion" by Tommy James and the Shondells, which was used in last year's finale.
The lyrics tie into the end of Walt's journey:
"I guess I got what I deserved" and "I would show the special love I have for you, my baby blue."
Show creator Vince Gilligan said the song ties into Walt's love for the blue drug.
"I think in that last scene, he was with his Precious,” Gilligan said, referencing The Lord of the Rings.
2014: The Year in Music [PHOTOS]