It turns out that worrying about who's going to knock on your front door has been a prominent fear for decades now. Eli Roth's Knock Knock is actually based on a 1977 horror-thriller film titled Death Game.
The film is roughly the same in its set-up, in that it follows a well to-do businessman, husband, and father, George Manning, played by Seymour Cassel, who's by himself for a weekend. Suddenly, two young women, played by Colleen Camp and Sondra Locke, end up knocking at his door, asking if they can get out of the rain by waiting inside. He accepts and soon finds himself being seduced by the attractive ladies.
While Knock Knock is the most recent adaptation of the film, Death Game was actually remade one other time in 1980, as the Spanish film Vicious and Nude, starring Jack Taylor, Eva Lyberten, and Adriana Vega.
Another fun fact about the 1977 film? A young Bill Paxton worked as a set decorator for it.
