Varian mentioned the events in Secret of the Sun Drop as part of his misdeeds, the time when he took Queen Arianna and he attacked Rapunzel.
Rapunzel mentioned the event of Queen for a Day that she has to stay when the kingdom needed her and Rapunzel also mentioned that she can't do anything about the amber.
Rapunzel also mentioned that she never meant to break her promise that she made to Varian.
Quirineon is the third of Varian's chemicals to be named after a person in this episode after Flynnoelum in What the Hair?! that was named after Eugene's persona and Cassandrium in Great Expotations that was named after Cassandra.