FULL SPOILERS ahead for the ending of Shazam!
That final scene featuring Superman isn’t the only DC character cameo at the end of Shazam!. The mid-end credits scene pays off an Easter egg planted earlier in the film by introducing viewers to Mister Mind, who is truly one of the strangest (and silliest) DC Comics supervillains ever.
A talking, evil alien worm with a genius-level intellect and hypnotic powers, Mister Mind is one of Shazam’s oldest adversaries, and a truly deep cut of a DC Comics reference. Briefly glimpsed earlier inside a glass case within the Rock of Eternity, that same case is later seen empty. These moments pay off in the mid-credits scene. As he furiously writes hieroglyphs on the walls of his cell — desperately trying to recalculate how to regain access to the magical powers he’s lost — Doctor Sivana (Mark Strong) is visited by none other than Mister Mind, who appears on the cell’s window ledge. (Shazam! director David F. Sandberg confirmed to IGN that he also voices the character.) The brief scene suggests a partnership of some kind between these two baddies is in the offering, with Mister Mind making a reference to the Seven Realms …
Source: IGN.com Shazam! End Credits Scene Explained