Throwback Thursday — or #TBT, as it’s commonly referred — has become a social media favorite. The fad caught on like wildfire, and now it’s impossible to scroll through Twitter, Instagram or Facebook without seeing friends, family members and our favorite celebrities sharing old school memories.

It's exciting to see celebs joining in on the #TBT fun, sharing with their fans old and never-before-seen photos. See what your favorite stars have posted this week, ranging from some cute baby photos to reminiscent pics from, uh… yesterday? Well, that still counts!

Kelly Osbourne and her younger brother Jack are looking blonde and adorable in this throwback!

We love when pop stars collide, even if we don't get the proof until years later. Lance Bass is all cuddled up to Beyonce and Michelle Williams in this oldie but goodie.

Jessica Biel is calling for the return of turtleneck sweaters in her woodsy #TBT.

Kevin McHale and Lea Michele were all over their shirtless 'Glee' costar Chord Overstreet...and we don't blame them.

Is that a choker necklace we see on Carly Rae Jepsen posing with little sis Katie? Very '80s/'90s --- we dig!

Beyonce posted a photo of herself surrounded by rose petals and Destiny's Child bandmates Kelly Rowland and Michelle Williams. Pretty fitting, considering just earlier today Michelle's leaked track 'Say Yes' revealed the three reunited for its recording.

Ellie Goulding is young and mustached in this throwback video of her and producer Starsmith making an album in a bedroom. Based on the song playing ('The Writer') it was likely her debut album 'Lights.'

Ludacris and Mystikal are mean mugging in this snapshot from the 2001 music video for 'Move B---.'

Lauren Conrad is looking too cute in her dress and tights while riding a big stuffed unicorn.

Emblem3 member Wesley Stromberg shared this shot of the band at tour rehearsals...just yesterday. He must've been feeling a little tongue-in-cheek when he posted the pic with the caption, "Ohh those were the days. The good old days."

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