The close of the Poseidonis scenes pokes fun at DC's propensity to include multiple characters and their legacies in the Justice League. At last count there were seven Green Lanterns in the various League teams (Hal, John, Guy, Teen, Kyle, Simon, Jessica, and now Jo Mullein) with two in the JSA (Alan Scott and his daughter Jade). Three Flashes have been Leaguers. Plus, of course, three named Aquaman at different times.
The credit scenes take place on 7/4/20.
Exactly one decade since the series started
It's not clarified if Lagann's child is biologically his or is the child of his husband and wife. It's a polygamous marriage, to clear up confusion.
Lagann is invited to the Justice League as Aquaman III.
It's notable that when Nabu is talking to Savage, Traci's voice lags in echo until Nabu speaks in plural; "we will not argue" is the only line they speak in-synch.