At one point during Bohemian Grove, Reagan holds up a sign that says "Bathroom" with an arrow. This was in "Party Down" which Liz Caplan and Adam Scott starred in, who plays a bit role as an Illuminati member.
Lin-Manuel Miranda says he'll be in "the room where it happens." This is not only the title of a song from 'Hamilton,' but also a reference to his status as a member of the elite Illuminati.
Regan and Ron are voiced by Lizzy Caplan and Adam Scott who starred together on Party Down. When Regan shows up to the Bohemian Grove she is wearing an outfit similar to her waitstaff outfit on Party Down.