Song: "Bad Blood," "Bad Blood (Taylor's Version)"
Album: "1989 (Taylor's Version) [Deluxe]"
Backstory: Swift's collaboration with Kendrick Lamar was teased in her September 2014 cover story for Rolling Stone, in which she also revealed that "Bad Blood" was inspired by a professional betrayal.
After a swarm of paparazzi and fans descended upon Swift in Central Park, which reporter Josh Eells described as "a little scary," Swift instructed him to listen to Lamar's "Backseat Freestyle."
"You want to know a trick to immediately go from feeling victimized to feeling awesome? This is my go-to," she said, adding, "I know every word."
The "Bad Blood" remix was promoted as a single in May 2015, seven months after "1989" was released. (It was never actually included on either tracklist for the standard or deluxe editions.)
"We both was in LA, so I came to her studio session. She had the music up and I started writing and jumped in the booth and we laid it down," Lamar recalled in 2017, praising Swift as an artist with a "great business mind and integrity."
"Fortunately, the vibe was right and it didn't take too many takes and we was really locked in on the chemistry and we really felt what was going on when I was in the booth," he added.
The Pulitzer Prize-winning rapper also appeared in the song's star-studded music video, which featured additional cameos from Selena Gomez, Karlie Kloss, Zendaya, and more.
Eight years later, Lamar returned to rerecord his feature, which was surprise-released with the deluxe edition of "1989 (Taylor's Version)."
"I still look back on this collaboration with so much pride and gratitude, for the ways Kendrick elevated the song and the way he treats everyone around him," Swift announced on social media. "The reality that Kendrick would go back in and re-record Bad Blood so that I could reclaim and own this work I'm so proud of is surreal and bewildering to me."