Organisers hope City of the Unexpected will turn the eyes of the world on the capital as landmarks are transformed over the weekend of September 17 and 18.
There will be road closures while Cardiff Castle, the city’s market, and the National Museum of Wales will all be part of the backdrop.
On the Sunday a huge Dahlian picnic will be held in Bute Park .
The event, produced by Wales Millennium Centre and National Theatre Wales , has just under 10,000 people involved so far and the capital is set to be taken over by the imagination of the renowned author.
The organisers have now put out a casting call for child roles in the extravaganza.
They are looking for a boy aged between 10 and 14 who is a confident speaker and natural performer with singing ability to play an 11-year-old schoolboy.
The casting call also notes the boy should be happy with heights, as they will be lifted up on a crane or a scissor lift, and will have two key scenes of around 20 minutes each.
They are also calling for a schoolgirl aged between eight and 11, who is a confident performer and singer, who will have a prominent solo in one of the newly-composed songs and will feature in several sections throughout the procession on a Saturday afternoon and civic welcome over a four-hour period.
Workshop auditions will take place from July 21 to July 22 in Cardiff with rehearsals over a couple of evenings and weekends in August and September – not in school time – before the event on September 17 and 18.
Anyone who would like their child to take part can email firstname.lastname@example.org with a full-length picture along with a head and shoulders shot as well as the child’s height, date of birth, and whether the child would be available for rehearsal dates and performance, with the subject line “School Boy” or “School Girl”.