Many of the geographical locations around Hawkins mentioned by Bob Newby (Sean Astin) such as Jordan Lake and the Eno River are named after real locations in North Carolina, located near Durham where the show's creators, the Duffer Brothers (Matt Duffer and Ross Duffer), grew up as children.
It's shown but not stated that Will's (Noah Schnapp) drawing is so large he actually uses up all the paper in the house; Bob (Sean Astin) has to do his calculations on an empty notepad and Joyce (Winona Ryder) marks Hopper's (David Harbour) location on the back of some wrapping paper.
There is a drawing of the white rabbit from Alice's Adventures in Wonderland on the wall in Jane's bedroom. Alice also travelled to an alternate reality like the Upside Down.
Although Max likes Lucas' version of the events of the previous year, she comments that she finds his story a little derivative and unoriginal, which was the showrunners' way of lampooning the criticism that the show itself has received on occasion.
Noah Schnapp researched medical texts about what happens to the body when a person has a seizure to prepare for shooting Will's reaction when the Hawkins Lab employees start burning to tunnels to the Upside Down.