Principal photography was shut down for two days when Sir Sean Connery contracted a respiratory condition during the filming of the mud sequence. The mud also knocked Connery off his feet, buried Karl Malden twice, while Natalie Wood was almost sucked into one of the pumps. During the mud filming, the actors and actresses would stuff their ears with cotton-wool, and had to have their eyes washed out, at the completion of each take.
Natalie Wood could speak fluent Russian in real life. Her parents were Russian immigrants and her birth name was Natalia Nikolaevna Zakharenko. Brian Keith was also fluent in Russian. However, he was not of Russian descent.
Several visual effects production teams were fired during the course of the lengthy production for failing to produce adequate effects on a very limited budget. The final company was forced to provide the effects seen in this movie for what money remained, seriously compromising the results.
The tidal wave sequence involved ten days of location filming in Hong Kong. For the scenes, eight thousand gallons of water were accidentally unleashed from two trip tanks at the same time (they were suppose to be consecutive releases) and eight people got swept away. No serious injuries resulted, only minor cuts, bumps, and bruises.
One of the final movies from "American International Pictures," this film's huge failure at the box office is considered to have contributed to the studio's downfall.
Henry Fonda: As the President of the U.S. Fonda shot his major cameo in two days. Fonda made a two-minute speech to the Washington Press Corp, which received a standing ovation from cast and crew, but was cut from the theatrical release. Fonda also played an unnamed American President in Limite de Segurança (1964), which provided several story elements for this movie.