Many of the 500 Florida frogs and 100 giant South American toads purchased for use in the film escaped during production.
In a review for "Andy Warhol's Interview", writer Fran Lebowitz called this movie "the best bad movie I have ever seen in my life."
Due to the film's low budget, no live birds were used for the bird attack scene. Footage of flying birds was superimposed over footage of the running cast.
Scenes of Sam Elliot shirtless helped him land the starring role in Lifeguard (1976).
Stephen King has mentioned this movie as the reason he decided on a topiary instead of a hedge maze in The Shining (1980). Stanley Kubrick could not get the topiary to work to his satisfaction, so he went with the hedge maze instead.
Because the film's poster art depicts a human hand hanging out of a huge frog's mouth, viewers often assume the film is about giant man-eating frogs, rather than swamp wildlife on the rampage.
The Florida Holiday Inn used by the crew would not allow the poisonous snakes, spiders, or black scorpions used in the film to be brought into the hotel.
A bedroom scene, in which Bella asks Kenneth to take her home, was scripted and shot but cut from the movie. Photographs of the scene, featuring a bare-chested Nicholas Cortland smoking a joint, were released with the film's press material.
Ray Milland wore a toupee throughout filming. He sweated so much that it fell off of his head several times.
This was the first of many "eco-horror" films of the 1970s, inspired by the surprise box-office success of Willard (1971).
The movie made the cover of Famous Monsters of Filmland magazine. The cover depicted a scowling frog with a human hand sticking out of its mouth, different from the film's poster.
The mansion used for the Crockett family home is the Wesley House, built in 1897. It's part of Eden Gardens State Park, in Santa Rosa Beach, Florida.
The large black and white lizards that attack Kenneth in the greenhouse are Tegus, native to Argentina. Several geckos and iguanas were also used for the scene.
Hollis Irving and Judy Pace both made appearances years before on Bewitched (1964). Irving in two epsiodes of season one and Pace in three of season two. Bewitched would come to an end just 15 days after this film's premiere.