Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
In this absurd comedy, Clint Eastwood is Philo Beddoe, a guy who fixes cars, lives with his mother, and makes money fighting in bare-knuckle fights for gamblers. His companions are a tow truck driver, his girlfriend who's a broke country singer, and an Orangutan named Clyde who hangs out in bars drinking beer, wears a watch, and likes to defecate in police cars. Clyde is also Philo's manager and handles his cash, and he tears apart cars on command with his bare hands. Even more absurd than Clyde's behavior is that we are expected to believe that Philo could withstand the number of bare-knuckle punches he receives and not end up with a face that looks like oatmeal and hands that are bloody stumps. Same goes for his opponents. The laws of cliche movie bar fights, where everybody is whacked many times and nobody suffers greatly, are in effect here.
The movie opens with Philo fighting a California Highway Patrolman in an industrial area with working class men doing the betting. Then it contrasts that fight by showing a group of well-dressed mobsters in a swanky hotel room in New York City betting tens of thousands of dollars on a fight between a Western Diamond-backed Rattlesnake and a mongoose inside a small plexiglass enclosure. The snake wins. The rest of the movie mostly involves Philo and a fight in Wyoming for him that is arranged by the New York mobsters, but there are also side plots involving Philo's romance, Clyde's romance with a female Orangutan they steal from the Bakersfield zoo, Philo's feud with a gang of incompetent Nazi bikers, mobsters double-crossing each other, and Philo's bromance with his fist-fighting opponent.
It looks like they couldn't find a cobra, the standard mongoose opponent, or even a mongoose, so they substituted a ferret. Unfortunately, the two animals were alive and actually fighting and it appears that the ferret was eventually struck and envenomated. We don't see it die, but it looks to be on the way.