In watching “The Shape of Water,” a new movie gaining popular and critical acclaim, Louisiana residents might notice a fleeting reference to Mardi Gras.

Directed by Mexican filmmaker Guillermo del Toro, the film chronicles an unlikely romance between a cleaning woman and a swamp thing who’s clearly inspired by “Creature from the Black Lagoon.”

Strange? You bet. But del Toro’s homage to 1950s science fiction includes a brief shout-out to another Cold War-era movie, the 1958 production “Mardi Gras.” The musical’s title appears on a marquee in a scene in “The Shape of Water,” which is worth noting since the meticulous del Toro fusses over every detail of his movies.

What’s del Toro trying to tell us with this little nod to Carnival? Maybe he’s reminding us that Mardi Gras, like his movies, are testaments to the awfully thin line that separates fantasy from fact. It’s a notion sure to resonate with local moviegoers as another Carnival season gets underway.