|Even with the increasing influence of television, the internet and social media, movies, primarily Hollywood movies, are still, and have long been, the main source of visual storytelling for Americans and possibly the entire world. This also means that they have been the main source of false information about herps, especially snakes, and if not the creator of them, then the main propagator of myths involving herps, the main ones being that all snakes are deadly and all snakes and crocodiles always want to kill people. It's the rare snake on screen that isn't demonized or used as a device to provoke some kind of terrified reaction.
Except for the obvious nature-run-amok or monster-snake movies on this list where herps are expected, most of these movies contain random herp sightings that I've come across watching movies. There are probably thousands more films with herps in them that are not on this list. The comments here are not meant to be full reviews of the movies, just descriptions of what are sometimes only minor incidents in the film that usually have little importance to the plot and even less effect on the quality of the film in general. In other words, this is some extreme movie trivia of questionable value that I put here mostly for my own enjoyment. Caveat lector.
Herps are secretive and rarely show up randomly in real life or in movies as often as birds or domesticated pets or barnyard animals, so when I see a herp in a movie, it usually sparks my interest. Even when a herp is just supposed to be part of the background in a movie, it has almost always been rented from a business that rents animals, sometimes a reptile zoo that uses animals they keep on display, brought onto the set, and intentionally filmed as part of the production, often under the guidance of an Animal Wrangler. Sometimes a director just uses some stock footage of wildlife to edit into the action or sends someone out to film them, but however they're filmed, they're not there by accident.
Snakes are by far the most commonly-used herps in movies, because of their symbolic power - lots of people are terrified of them - and because, since there are snakes capable of harming and killing people, they can be used as a convenient evil adversary or obstacle for a character to overcome. That's why so many rattlesnakes show up in Westerns and other movies. The audience is already pre-disposed to believe that all snakes are a dangerous threat because of all the evil snakes they've seen in movies and TV. They myth is so prevalent and longstanding that it is now accepted as truth. Snakes add tension and a little extra drama, like a gun, a car chase, or sexual attraction, but to me they usually come across as just an artificial addition inserted only for the convenience of the plot and rarely represent any kind of realism in nature. (Even in Westerns and jungle adventure films which take place in snake-rich areas.) Snakes in movies are almost always used unrealistically and they are almost aways egregiously misrepresented. Maybe we have the Bible's Adam and Eve story to blame for that, but it probably goes even farther back in time than the bible.
Crocodilians are also used almost exclusively to represent a deadly threat, since they are capable of killing humans. Gila Monsters show up sometimes as representing a threat, but the presence of most other kinds of herps in movies is usually only incidental to the plot, whether they are seen as a wild animal or as a pet. In most cases, they seem to be added for their creepiness factor and rarely as they would show up in the real world. Since the explosion in popularity of keeping herps as pets, beginning roughly in the 1980s, there have been many more
pet herps shown on film often as a child's pet shown in the background.
Herps have also been faked on film in many different ways that have improved in believability as the special effects industry has developed, including Melies' use of false perspective to shownewts in an aquarium as monsters, double-exposures, stop-motion, claymation, animation, live animals painted or fitted with extra horns or spines, computer generated effects, and just plain fake rubber animals pulled on strings or simply as static background fillers.
The links above will take you to lists of movies that themselves lead to pages full of pictures and movie information.