Hundreds of people turned up to the casting with some having to be turned away
More than 1,000 people lined up for a chance to appear with Hollywood stars Russell Crowe and Cate Blanchett.
Director Sir Ridley Scott was looking for 600 extras to play soldiers in his new production of Robin Hood.
Hundreds had to be turned away from the Technium Centre in Pembroke Dock which was the venue for the open casting because of such a high turn out.
Technium manager David Thomas said: "It's totally alien to anything we do but it was an opportunity to help out."
Oscar-winning actors Crowe and Blanchett star as Robin Hood and Maid Marian in the film to be shot on location at Freshwater Bay in Pembrokeshire National Park.
The film, which had been called Nottingham, is said to have a $130m (£91m) budget.
The extras, as soldiers, will be up against Russell Crowe as Robin Hood
Having landed the top billing, Sir Ridley, who directed Crowe in the 2000 block-buster, Gladiator, is recruiting a small army of extras to play the Sheriff of Nottingham's men. A London-based casting agency ran the open day.
But a higher than expected number of people turned up and many were turned away. However they were told to apply online.
Speaking before the casting, Technium manager David Thomas said he thought the technology and innovation business centre had been chosen because of its size.
"There's a huge open area to receive a very large number of people.
"It's a very straightforward process. They will basically form an orderly queue. They will be seeing up to 800 people.
"They will measure them for costumes, photograph them, and answer any questions. The photos will go to the casting director.
"There are no auditions or anything like that. They need 600 soldiers, so it is just for extras."
It is expected that some battle scenes will be filmed at Freshwater West
Filming is to take place at the end of June and into the first week of July. Again there should only be a small amount of disruption, and a few minor road closures.
Pembrokeshire National Park has said it expects filming to take place at the end of June and into the first week of July.
Freshwater West is also being used as a location for the final film in the Harry Potter series.
Road closures will be in place for the filming of Harry Potter and the Deathly Hallows between 11-15 May, although it is believed that filming could lasting until mid June.
The park authority said while filming would cause some disruption, the beach and coastal path will be kept open.