Directors love placing subtle callbacks to their previous films, especially if those movies helped their careers take off. For example, Sam Raimi almost always finds a part for Bruce Campbell, who helped kick off the Evil Dead franchise back in 1981.
For David F. Sandberg, that previous project is Lights Out, the 2016 low-budget horror film that debuted to critical and box office success. This helped Sandberg land the job of making Annabelle: Creation a year later, which also fared well with audiences and critics.
Sandberg's biggest project yet will be next year's Shazam!, an addition to the DC Extended Universe at Warner Brothers, which helped finance his previous two movies; they most likely gave him the DC title based on his strong track record. When asked on Twitter if we'd ever see an Annabelle/Shazam! crossover, Sandberg confirmed that not only would there be an Annabelle Easter egg in the superhero movie, but there will also be a character from Lights Out making an appearance.
"So, you could argue that they take place in the same universe," wrote the director.
According to speculation from Screen Rant, the Lights Out character most likely to show up in Shazam! is Esther, who is played by Lotta Losten, Sandberg's real-world wife. Since she was the only actress to appear in the feature-length version and the 2013 short film that inspired it, odds are good that she's the character that bridges these two universes together. Moreover, Losten reportedly appeared "in film listings for Shazam! as an unnamed character."
Shazam! arrives in theaters April 5, 2019. Asher Angel portrays young Billy Batson, a boy who gains the power to turn into an adult superhero (Zachary Levi), just by speaking the world "SHAZAM!" Mark Strong (Dr. Thaddeus Sivana), Ron Cephas Jones (the wizard Shazam), Grace Fulton (Mary Bromfield), Jack Dylan Grazer (Frederick "Freddy" Freeman), and Ian Chen (Eugene Choi) will star alongside Angel and Levi.