Paul Reiser and Kelly McGillis were replaced after a week of shooting had been completed (which followed a week of rehearsals). Reiser and McGillis were replaced by the head of the studio (20th Century Fox) who at the time was Joe Wizan. The director was very happy with his cast but Mr. Wizan insisted. The production temporarily shut down, the rest of the cast was kept on payroll for a three week period while actors were screen tested for the two lead roles. Tawny Kitean was cast from those screen tests. The actors who tested, among them the late Dino Martin, Jr. and David Naughton (American Warewolf in London, Dr Pepper commercials), were not cast.
Tom Hanks did not screen test. But, after having passed on the role a few months earlier (before Reiser was cast), Hanks was again approached and offered the role. This time Hanks accepted, the character's name was changed from Richie to Ricky, and he was paid $15,000 a week. He had already shot 'Splash' but it was not yet released. Some months after principal photography was completed, there was a day or two of additional filming. By then, 'Splash' had been released and was a hit...and Hanks was, to the delight of the producers, a new movie star.