In 2001, Britney Spears and her then-boyfriend Justin Timberlake left an indelible mark on the world of red carpet fashion when they rocked matching denim ensembles to the American Music Awards.
While the outfits aren't identical – not really even close – it's clear that they were poking gentle, loving fun at the "Toxic" singer and the former 'N Sync member.
So how did Britney react to their playful jest? Really nicely, actually. The "Piece Of Me" singer tweeted at Perry: "Just when I thought the denim dress had retired....you bring it back! You looked amazing tonight."
Katy went on to win the MTV VMA moonman statue early in the night for Best Female Video for "Dark Horse" featuring Juicy J, and the beautiful singer accepted the award while still decked out in head-to-toe denim.
Check out all the fashion throwbacks that dominated the red carpet in the video below...