FULL SPOILERS ahead for Shazam!
The very last scene in Shazam! before the end credits roll features the film’s biggest DC Comics cameo — but not in the way fans may have expected. Yes, as had been rumored and hoped for, Superman appears in Shazam! … from the neck down. And it’s not Henry Cavill playing him, although the costume might certainly make some viewers think it’s him.
In the spirit of the movie’s theme of wish fulfillment, the last scene sees in-universe DC fanboy Freddy Freeman (played by Jack Dylan Grazer) meeting his idol Superman thanks to his foster brother Billy Batson’s alter ego, Shazam (played by Zachary Levi). Freddy had previously bragged to his Fawcett High classmates that he could get his pal Shazam to show up at their school for lunch. But when Shazam failed to appear, Freddy paid the price for it in public humiliation.
Source: IGN.com Let's Talk About THAT DC Cameo in Shazam!