Trivia: The original ending for this film (fully produced but then deleted) was a jaw-dropping apocalypse. For starters, Audrey II actually kills and eats both Seymour Krelborn and his bride-to-be, Audrey. The giant carnivorous plant grows to gargantuan proportions and divides into multiple monsters that go on a Godzilla-style rampage across New York City, tearing down bridges, eating whole passenger trains, climbing the Statue of Liberty, and doing battle with the military. The original ending alone cost over $5 million out of the film's $25 million budget, so it was a major undertaking. When director Frank Oz test-screened the finished film, he was stunned that audiences hated the deaths of lovable Seymour and Audrey and everything thereafter. Oz hastily reassembled his cast and crew to re-shoot a cheaper, much less gruesome happy ending, which was a hit with audiences. However, Frank Oz said that he thought the original ending was far superior and some of his best work, and he was extremely dissatisfied with the revised happy ending.
Trivia: To make the effects of Audrey II look convincing, the animatronic was usually shot at a lower frame-rate, such as 12 frames per second, and then played back at the standard 24fps. This sped-up the shots and made the animatronic's motions look more fluid and lifelike. In order to compensate, whenever a human actor would be in-shot with Audrey II, they would have to act in "slow motion" in order for their movement to look right at 24fps. (You can kinda tell in a few shots if you look closely).
Answer: Most likely it is referring to It! The Terror from Beyond Space (1958) or possibly It Came from Outer Space (1953).