We just love the enthusiasm from these famous faces and their kids who shared their costume creations on their Instagram pages.
Take a look at some of these fun outfits below and keep scrolling because there's a surprise from author David Walliams!
WATCH: Amanda Holden is the Queen of Hearts for World Book day
Rochelle Humes' daughter Alaia-Mai
Alaia-Mai Humes as Willy Wonka
Such a cute outfit here on Rochelle and Marvin Humes' daughter Alaia-Mai, who dressed up as Willy Wonka from the iconic book Charlie and the Chocolate Factory.
Rochelle wrote: "Happpyyyyyy World Book Day. Oh, you better worrrkkkk it Willy Wonka."
Myleene Klass' daughter Hero
Myleene Klass' daughter Hero
TV presenter Myleene gets our top effort award for this amazing costume! Her daughter Hero dressed up as a red crayon from the book The Day the Crayons Quit.
Myleene posted: "Happy #worldbookday from ‘the angry’ red crayon."
Vogue Williams' son Theodore
Little Theodore as a bee!
Oh, what a sweetie! Vogue Williams and Spencer Matthews' son Theodore made the cutest bee we've ever seen for World Book Day.
Vogue told fans: "He was meant to be a dinosaur but our package didn't arrive! A bee it is!"
Denise Van Outen's daughter Betsy
Betsy as Veruca Salt
Sweet Betsy needs to team up with Rochelle Humes' daughter Alai-Mai as they both dressed up in Charlie and the Chocolate Factory themed outfits for World Book Day this year.
Mum Denise wrote: "World Book Day 2021 Betsy, Veruca Salt - Charlie And The Chocolate Factory." One fan wrote: "Love it so much!!"
A brilliant touch with the golden ticket and Wonka chocolate bar!
Frankie Bridge's children Parker and Carter
Frankie's sons dressed as animals
Former Saturdays singer Frankie shared this snap of her sons getting in the World book Day spirit as a leopard and a spider.
Frankie said: "So... luckily for me @myleeneklasskids loves a bit of leopard print and @nextofficial does next day delivery. I am also VERY lucky... to have a mother in law who happens to be very creative!... as I wouldn’t have known where to bloomin start with a spider?! The kids have worn them for 5 mins on zoom and have now removed them, well done parents for doing your homework. A* all round!"
Tamara Ecclestone's daughter Sophia
Sweet Sophia with her unicorns book
Aw, this is so bright and cheerful! Tamara Ecclestone's daughter Sophia dressed up as the character from her favourite book There's No Such Thing As Unicorns.
Tamara's fans adored Sophia's fun costume, with one telling her: "Love her outfit, you look great Fifi." Another follower said: "So cute - I remember when you said she wanted a unicorn for Christmas and you said you are getting her this book @tamaraecclestoneofficial those tights are everything. X"
And the amazing David Walliams!
David Walliams got into character!
Encapsulating what World Book Day is all about, the wonderful author David Walliams dressed up as his own character Burt from his book Rat Burger! "Happy #WorldBookDay from Burt from 'Ratburger'," posted the star.
On David's Instagram Stories, the writer had shared scored of photos from his child fans all dressed up as his book characters to celebrate the special day. Amazing stuff David!