Oliver refers to Max Fuller having him and Tommy beaten up and thrown out of his club; this occurred in episode 1x3 "Lone Gunmen."
The sweater top that Felicity wears in the opening scene is the same sweater that Iris wears in the first scene of Elseworlds, Part 1 (2018).
At 3:37 Oliver quotes a line from his wedding vows to Felicity, saying "You will always be the best part of me, for the rest of my life."
At 11:11 there is an error in the English subtitles on the video disc. "The arrows are consistent with the vigilants". "vigilants (plural)" should be "vigilant's (belonging to/possessive)".