This wasn't a random guest appearance on Friday night (7 July) as all three also feature in Swift's new music video for her 'From The Vault' track 'I Can See You' which premiered at the concert.
In the video, both Lautner and King are burglars, and with help from Cash, they break into a museum filled with dresses and props from Swift's career over the years, where they also show off their fighting skills as security tries to stop them.
The pair eventually make it to the vault, where they break free Swift (dressed in her Speak Now era look), who had been trapped inside, and she takes with her the framed picture of the cover art for her new version of her third studio album.
The three of them bolt out of the museum as explosions set off but make it to the van as Cash drives them away from the scene.
As Swift loves giving fans Easter eggs, fans have noted how the three actors have previous connections to Swift's Speak Now era.
The two Taylors famously dated back in 2009 for a few months after they starred together in the romantic comedy Valentine's Day, where they played a couple.
It is widely speculated that the breakup song 'Back to December' from the album is about Lautner, with the theme of the song about apologising and asking for forgiveness from an ex for breaking their heart.
Meanwhile, King and Cash both appeared in Swift's music video for the track 'Mean'.
Swift explained in an Instagram post that the music video she wrote and directed was about wanting to "play out symbolically how it’s felt for me to have the fans helping me reclaim my music."