Character mistake: Barbara is in her office looking for the one item they need help to identify when Diana walks in. She says "OK, item number 23." She suddenly finds it saying "here it is" and reaches in the box to grab the Dreamstone. The ticket says item #24. (00:22:18 - 00:22:50)
Character mistake: There are signs out front as the Spenglers arrive at the dirt farm. One of the signs is a call back to a scene in Ghostbusters 1984. In the scene, Ray quotes the book of Revelation: "And I looked, and he opened the sixth seal, and lo, there was a great earthquake. And the sun turned black as sack cloth, and the moon turned blood." When Finn Wolfhard reads it he misquotes the line saying "The sun became as black as cloth."
Character mistake: They keep calling the vehicle a milk truck but it says "ice cream" on it. (00:23:55)