Caitlin mentions wanting to go to Mapleville, referencing Adventure Comics #461 (1978) "The Multiple Murders of Mapleville," in which on a trip through a small town with Iris, Barry Allen is somehow compelled to use a gun on a man, and is framed for murder.
Chester uses the expression, "Great Otis Boykin!" Otis Boykin was an African-Amerian electrical engineer who invented resistors and electrical control devices used in guided missiles, computers, transistor radios, and pacemakers.
Allegra mentioned to Chester during his live stream that her grandmother used to refer to death as "noche mas negra," or "The Blackest Night." This could be a reference to the 2009 D.C. Comic of the same name. It involves the supervillain Nekron, who is the embodiment of death and can reanimate the dead. Nekron resurrected Firestorm during this event and created Deathstorm.