Ursula Andress visited the set on the first day of shooting. Moreover, it was freezing cold on the first day of shooting in Austria. Rumor has it that she really only appeared on the set in order to keep an eye on her then partner, Fabio Testi, and British actress, Lynne Frederick, as she suspected he was cheating on her. There was much speculation about such an affair, but the truth of it is still unknown.
Lynne Frederick (Bunny) and Fabio Testi (Stubby) were smitten with each other during filming, naturally helping their chemistry in the movie. In the aftermath of Frederick's blacklisting in Hollywood, Testi is one of the few people who continues to publicly to speak fondly of her.
Fabio Testi and Lynne Frederick were so reluctant to end their time with each other for the film that during their final shared scene (Bunny's death), one of them would keep requesting another take for all sorts of made up reasons. They even improvised on a few takes with Testi's character (Stubby) kissing Frederick's character (Bunny) before her death, but this was not used in the final cut of the film.
Two scenes where deleted from the final cut of the film. One of them was after Chaco leaves the group for dead, an injured Clem crawls on his wounded leg and unties Stubby. This scene was deleted because it dragged the film on. Despite the fact the scene was deleted it was seen on one of the lobby cards issued for the film. The other scene omitted from the film was a full blown love scene between Stubby and Bunny, but it was deleted because it was considered excess. To this day the scenes are considered lost or have yet to be discovered.
In order to make her look pregnant, Lynne Frederick had to have additional padding fitted into her costumes as she was naturally very slim. During the scene where she was nude, her slimmer frame was obviously noticeable so the director instructed her to slouch forward, curl up, and have her long hair in front of her.