The way David F. Sandberg presents this behind the scenes is funny, because when you first see him with his head covered in some kind of mold, you start wracking your brain trying to remember the movie and figure out what this cameo could possibly be. Or at least I did. The director was clearly getting fitted for some sort of molded costume and as you scroll through his Instagram pictures, you discover what that costume was.
Article source: https://www.cinemablend.com/news/2470247/shazam-director-reveals-behind-the-scenes-look-at-his-cameo