Shazam! (DC superhero movie) is set in the same fictional universe as Lights Out, the 2016 horror film based off the 2013 short film of the same name.
Link to the original short film on YouTube. CW: It's a horror film! https://www.youtube.com/watch?v=-fDzdDfviLI
CW again, it's horror!
I watched it, got thoroughly spooked, and decided to search more about it. Turns out there was a full-length film made, also called Lights Out.
https://en.wikipedia.org/wiki/Lights_Out_(2016_film)
In June 2018, Sandberg stated that his then-upcoming film Shazam! would be set in the same fictional universe as Lights Out, featuring a character from that film in a cameo appearance.
jaidedctrl wrote
Ahhh, I loved that movie!
It's pretty cool that they're in the same universe… but why? Jajaja