Sylvester mentions The Crimson Avenger. This was one of DC's earliest costumed heroes, and a founding member of The Seven Soldiers of Victory - a superhero team that included Sylvester Pemberton and Pat Dugan as Star-Spangled Kid and Stripesy. The team and its members have been mentioned or featured in previous episodes.
Hakeem mentions seeing "crocodile people". In the movie Shazam! (2019) one of the doors in the Rock of Eternity opens on a group of "crocodile people" playing cards.