Over 13,000 Rick and Morty fans unexpectedly suffered an intense and bizarre food craving after the hit animated series aired its third season premiere on April 1. No, it wasn’t (only) just a bad case of the munchies; it was the powerful effect of one excellently executed feat of psychological manipulation. Nobody had thought about McDonald’s Szechuan dipping sauce for two decades, but after Rick revealed that all of his adventures were geared toward tasting the fabled sauce, it was the only thing on viewers’ minds.

Their brains didn’t stand a chance.

While the psychological effect of product placement on consumer cravings is hardly a new phenomenon, Rick and Morty presents an excellent example of “affective conditioning” done right. Psychologists use this term to describe the transfer of our feelings from one thing to another, which is exactly what happened to people who watched the episode. Most viewers, having not thought about Szechuan sauce since McDonald’s introduced it as a Mulan promo in 1998, likely had neutral feelings toward it, but when they saw it juxtaposed with characters and scenarios they felt positively about, their attitudes likewise shifted toward the positive.

Whether it’s being employed in an animated series or a Super Bowl ad campaign, this tactic is super effective, as a 2010 study in the Journal of Consumer Research illustrated. In the study, psychologists had people choose between two brands of pens. The participants were told, straight up, that one brand was better than the other. But this knowledge didn’t matter when participants saw photos of the pens preceded by a flashing image showing positive items.

“This creates an ‘I like it, but I don’t know why’ effect,” the researchers wrote, explaining that people picked the pen associated with the positive items 70 to 80 percent of the time, even if it was the bad pen. These secret, rapidly formed feelings they develop about the pen are called “implicit attitudes,” and they’re the same subset of feelings that likely led to the uptick in Szechuan sauce interest. In the Rick and Morty experiment, Rick was the flashing positive image, and Szechuan sauce the pen.

Taking this idea further, University of Minnesota-Duluth psychologist Ian Zimmerman explained in a 2013 article in Psychology Today that TV characters can lead to “implicit self identification.” In the article, he wrote that “when we watch a liked character use a brand, we can start to automatically identify with the brand as a way to vicariously experience that character’s life.”

Gaming viewers’ brains to form positive implicit attitudes about products is the primary goal of any advertiser, and it works because it reaches us on an emotional level. In his book Descartes’ Error, University of Southern California neuroscientist Antonio Damasio argued that our emotions are the most important factor in making decisions — which Rene Descartes, master of cold reason, famously disagreed with. Damasio studied people whose brain injuries severed the parts of their brain related to emotions and reasoning and discovered that they were unable to make decisions because they couldn’t feel. Conversely, any Rick and Morty fan, feeling strongly about Rick, implicitly knew how to feel about his dipping sauce preferences.

But perhaps more importantly, the fact that Rick and Morty fans weren’t explicitly aware of what was going on psychologically may be what led their Szechuan craving to be so intense. As the authors of the pen study pointed out, affective conditioning is most effective when people aren’t really paying attention to what’s happening. While viewers may have assumed during the episode that the McDonald’s cameo was merely another of the show’s signature nonsequiturs, they likely realized soon afterward that it was so much more than that. While there’s no official partnership between McDonald’s and Rick and Morty, the show’s Twitter account is now making a genuine push to get the fast-food chain to bring Szechuan sauce back — and it seems to be working.