Some of the best horror films succeed due to a simple plot, perfectly timed suspense and great actors. However, within that simplicity is an opportunity for fans to find ways to make their favorite films and characters connect in unlikely ways. This could be through a killer's shared motivations or literal in-universe connections that tie them together. One of the best examples of this is Alfred Hitchcock's 1960 film Psycho and John Carpenter's Halloween.
According to one theory, Psycho's Sam Loomis is the same character that later appears in Halloween as Michael's psychologist. While there is no concrete evidence to back the theory, the story of how the boyfriend of Bate's victim becomes obsessed with stopping Michael Myers is nothing short of intriguing. Not to mention the nearly 20-year gap between the two films fits perfectly with the natural progression of character.
In Psycho, Sam Loomis finds his way to the Bates Motel while looking for a private investigator who's trying to locate Loomis' missing girlfriend, Marion Crane. Instead, Loomis finds the deranged Norman Bates, who has killed the private investigator and Marion. After Loomis subdues Norman, he is taken away by the police.
This is where the connection to Carpenter's Halloween film begins. The theory is based on the idea that after such a traumatic experience, Loomis is driven to learn more about criminal psychology. Focusing his anger and sadness at the death of Marion, he goes to school with the goal of understanding killers like Norman and what causes them to tick. Taking an internship at Smith's Grove Sanitarium, he pivots his focus toward child psychology, where he is introduced to a young Michael Myers.
In Halloween, Michael murders his sister in cold blood and spends the next couple of decades locked away under Loomis' watch. Sam sees Michael as a chance to give meaning to Marion's death and does his best to understand the mind and motivations of the killer. Ultimately, he concludes that there is no motive for Michael's actions, and, unlike Norman, he is just evil for the sake of being evil. This turns Loomis' attempts to understand him into a mission to keep him from harming anyone else. The stress Michael causes on Loomis also explains his hair loss and weight gain while justifying his uncharacteristic need to hunt down his patient, killing him if necessary.
The real reason Halloween share's the name Sam Loomis is probably a homage to Psycho and the fact that Jamie Lee Curtis' mother played Marion. However, it's an intriguing theory to consider that the man who tragically lost his girlfriend strives to make sense of her death and inadvertently plays a part in the deaths of others through Michael. It not only justifies why he is relentless in hunting him down for five films but also brings an unlikely similarity to two of horror's most iconic films.