He wasn't aware of any celebrity appearances, but added that former Black Caps captain Brendon McCullum may well turn up.
The real celebrities of the day will be the racehorses, Mr Castles saying Gingernuts would be racing at the carnival with a 60-strong travelling entourage.
"They all wear their red caps with 'G-Nuts' on them. Hopefully, he can be competitive and deliver in the main race."
With ticket sales soaring this year the chief executive put the event's popularity down to people wanting a "break-out" event after a long winter.
"People are looking for an opportunity to dress up and have a social event. This race day is a Hawke's Bay institution.
"So many Hawke's Bay people come back to the Bay for the weekend. They come back to catch up with friends and family and have an enjoyable day at the races. We just need that Hawke's Bay weather that we love so much to play its part and it'll be a cracking day."
Mr Castles was really looking forward to the racing, particularly the Sacred Falls Hawke's Bay Guineas which had an "outstanding field" this year.
"I also look forward to catching up with trainers from all around New Zealand that bring their horses this day to try and claim some of the good stake money on offer."
The Bay Ford New Zealand Punter of the Year competition also drew people from throughout the country, with the chance to claim a $20,000 cash prize, he said.
"We encourage people to get a ride to the races or drive responsibly. We have ATM machines here but bringing cash is a good option rather than lining up to get cash," he said.
Gates open at 11am today with the first race beginning at 12.37pm. More information can be found at www.hawkesbayracing.co.nz/events/views/61.