Happy Throwback Thursday! As is now customary, everyone flocked to social media today to share cute, funny and never-before-seen photos from previous years. Celebs joined in on the fun, sharing their own blast-from-the-past moments with fans and fellow stars.

We've collected this week's best celebrity #TBT photos for you to check out. Take a look at the throwbacks that Hilary Duff, Kelly Osbourne and more shared today!

This adorable baby rocking a big hat is none other than Ludacris.

Hilary Duff threw it back to 1998 when she starred as Wendy in 'Casper Meets Wendy.' It's been 16 years and she still looks exactly the same!

AnnaSophia Robb spent her #TBT remembering when she first brought home her cute pup Sir Fergusson. (And what a perfect name for a puppy!)

'Dancing With the Stars' champ Julianne Hough dropped this video of her at a shooting range in Washington, D.C.

Melissa Joan Hart shared this epic #TBT of her and her costars on the set of 'Sabrina the Teenage Witch' filming the classic episode 'Murder on the Halloween Express.'

Victoria Justice posted an awesome old snapshot of the 'Victorious' cast with the 'iCarly' cast. (Nice cameo from Ariana Grande!)

Kelly Osbourne doesn't look too thrilled in this funny photo of her as a newborn with rocker dad Ozzy Osbourne.

Remember the days of popped collars? Fall Out Boy certainly do!