The 'Fireworks' singer was joined by rapper Riff Raff at the LA ceremony this weekend (24 August), and the twosome matched their looks by both sporting head-to-toe denim...
But we had a serious case of déjà vu as soon as we saw their ensembles - who remembers Britney Spears and Justin Timberlake wearing almost identical getups to the American Music Awards back in 2001?!
Pretty much the only differences between K-Pez and Britters' frocks were the bling-tastic silver studs and racy thigh-high slit on Katy's number.
Meanwhile, Riff Raff also amped up the glitz factor by adorning his suit with sparkling studs, adding a shimmering silver top, dazzling necklaces and cornrow braids (although we have to say, we preferred JT's cute curly ringlets).
But, unsurprisingly, their lookalike outfits weren't just a coincidence - of course Katy planned the whole thing.
Taking to Twitter earlier that night, the starlet wrote: "I must admit my outfit is a result of my love for nostalgia and my tumblr addiction #THISISHOWWEDOVMAS."
She later addressed Britney directly, saying: ". @britneyspears I did my best impression, hope u likey!"
Thankfully pop royalty Brit saw the funny side of things, replying to her pal: ".@katyperry Just when I thought the denim dress had retired....you bring it back! You looked amazing tonight bb ;)."
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Watch Britney's video for '...Baby One More Time' below: