She added the pic with a funny caption, "This is what happens when you admit on TV that you don't know any NSYNC songs and you're married to @justintimberlake. Well played, husband, well played."
Biel is referring to her recent appearance on The Tonight Show, where she admitted she didn't know a single lyric to any of the songs that jumpstarted his career. "I only know three words, 'Bye, bye, bye.' Which I guess is just one word three times," she told Jimmy Fallon.
Despite the confession, the 7th Heaven star was ready to transform into everyone's favorite late '90s heartthrob. Biel wore a curly blonde wig, a jumpsuit and even captured the perfect pose to make the resemblance uncanny. Her husband (as to not outshine his wife's amazing costume) dressed like a huge microphone, giving off major Saturday Night Live vibes.
He also added the photo on his own Instagram, along with a group shot of "NSYNC" with Biel in the middle. Timberlake's caption mirrored hers, poking fun at The Tonight Show interview, "This is what happens when your wife admits on TV that she doesn't know any NSYNC songs."
Her post got over 600,000 likes and virtual standing ovations for the Halloween idea. However, this isn't the first time the couple had matching costumes. Last year, they dressed as Batman character Legos, along with their then 3-year-old son Silas.
While their son is still too young to learn "Bye, Bye, Bye" or "It's Gonna Be Me," we can only hope his reaction to his mom's costume was a good one.