The prisoner number on Oliver's shirt during the party is 399471 which is a hex color for green that closely matches his hood.
When Oliver's mugshot is being taken, his prisoner number 73 1941, the issue number and year of his first appearance in the comics, in More Fun Comics #73.
When Oliver and Laurel walk into a bedroom in the Queen mansion, Laurel remarks that she can't remember the last time they were in there together and Oliver says it was when they were getting ready for Tommy's Halloween party. Laurel then says "Right, those fishnet stockings. I don't know what I was thinking." This is a reference to the comics where, as her alter ego Black Canary, the classic costume includes fishnet stockings.
This marks the first episode we see Diggle in the Arrow suit.
Oliver Queen was born on May 16, 1985.