During flashback sequences, references are made to several JSA members who have yet to appear in this series. This includes: the Spectre, Dr. Fate and " the Hawks", i.e. Hawkman and Hawkgirl/Hawkwoman. Versions of some of these characters have previously appeared in other "Arrowverse" shows.
In the flashbacks, the JSA treats Pat like a hired hand (You're just the mechanic) and Sylvester acts like he is subordinate to him. In the comics, the JSA acknowledged him as an equal and he was a partner and mentor to the Star-Spangled Kid.
When Pat closes the trunk containing old JSA files, it can be seen that his former address was "1941 Siegel Way". This is clearly a reference to the year that the Star-Spangled Kid/Sylvester Pemebrton and Stripsey/Pat Dugan debuted, as well as their co-creator, Jerry Siegel (who also co-created Superman).
In the prelude the paper in the manual typewriter displays "LOST SOCIETIES"/by/Bruce Gordon".
Pat sends Mike to the attic to get sleeping bags for the family to use as they wait out the storm in the basement. Mike brings down two bags for the family of four.