World Book Day was celebrated by children across the UK on Thursday, as over half a million aspiring young writers dressed up as their favorite characters from books to watch their favorite authors talk about how it's done.

The hour-long World Book Day event, billed as "The Biggest Book Show On Earth," took place at 11 a.m. Thursday morning and included children's authors Francesca Simon, Anthony Horowitz, Lauren Child and Tony Robinson, according to UK publication The Guardian.

"The Biggest Book Show On Earth," was shown in movie theaters and was streaming live online for World Book Day.

Robinson who created the "Horrid Henry" series, hosted the event.

"The target this year is for three quarters of a million children," the host said Wednesday in anticipation of the World Book Day event. "I'm just about to go and sit in a quiet place and start to think about what I'm going to say. It's the largest audience I've ever played to."

Liz Pichon of "Tom Gates" fame, said she will offering young aspiring writers advice about structure.

"I'll be talking about how to capture your ideas and plan your writing," Pichon said.

Schools and libraries across England will also be participating in World Book Day, which is also open to literary fans.

Pichon thinks it is a great way to encourage kids to read.

"Most schools these days almost have a World Book Week, with events going on throughout the week, book fairs, dressing up," Pichon said. "Everyone gets involved. Anything which encourages children to pick up a book of any kind is fantastic. It really makes a difference and gets them to try out something different."

World Book Day organizers also launched a cellphone app Thursday aimed at young adults. The app features stories from top teen writers like Chris Ryan, Patrick Ness and Alex Scarrow, as well as up-and-coming wordsmiths from online writing community Movellas.

"The new app and our partnership with Movellas is just one way of getting great book content to young adult readers," said Kirsten Grant, director of World Book Day. "Delivering content digitally and talking to teens in the spaces they like to visit and socialize also allows us to offer a taste of the brilliant fiction that's out there and hopefully, turn more young people on to reading."

See children's book "The Cat Inspector" read by author Katie Fryd for World Book Day.