Towards the end of her career, Joan Crawford seemingly had two requirements for any role she took- the check had to clear and the studio had to let her promote Pepsi, on whose board she sat after the death of her husband. Trog satisfied both of these requirements.
The troglodyte of the title was not Ms. Crawford, but her co-star, a man in a Bigfoot suit who her character discovers in a cave. Joan plays an anthropologist who discovers "Trog" and gets the task of spouting the technobabble dialogue that pushes the story (such as it was) along. Along the way, we get shots of Ms. Crawford and Trog enjoying Pepsi and learning from each other.
The film was typical of the sci-fi movies of the 1950's. Too bad it was being released in 1970. With Joan's needs met, however, she cared little for the film's success or failure.
Subtle product placement!