At 46:50, Hopper empties his clip into the Russian assassin hunting him. The slide can be seen hooked up to the pistol's slide stop, indicating he's out of ammo. He never picks up another clip, yet he keeps the gun as if loaded.
In Back to the Future (1985), Marty's "you built a time machine" line happens shortly before Einstein returns to the present. In the screening seen in this episode, that line is heard just after it, even though most of the rest of the scene it's part of (stainless steel construction, etc.) is heard in its proper place.
Steve and Robin comment on Lorraine's attraction to her son in Back to the Future (1985) after they've suddenly left the theater. The episode implies that they leave in the few minutes Dustin has gone to the booth right after the time travel is first shown, but the earliest sign of Lorraine's attraction to Marty is twenty minutes away.
In season 3, Lucas was referring to the movie "The Thing" (1982) as to how good it was, but the re-make of the movie stinks. The re-make was done in 2011! Setting of this series was supposed to be in 1983.
CORRECTION: The remake that Lucas was referring to was not the 2011 one, and the original he was referring to was not the 1982 one. Lucas was actually referring to the original "The Thing From Another World" (1951), and the remake being "The Thing" (1982)
CORRECTION: The remake that Lucas was referring to was not the 2011 one, and the original he was referring to was not the 1982 one. Lucas was actually referring to the original "The Thing From Another World" (1951), and the remake being "The Thing" (1982)
The song "R.O.C.K. in the U.S.A." plays during the opening scene. The scene is set on July 4th, 1985. However, while "R.O.C.K. in the U.S.A." was on John Cougar Mellencamp's album "Scarecrow," which was not released until a month later, on August 5, 1985, the song does not appear to be playing in universe.
When Lucas and Will are in the cereal aisle at Big Buy, there is a single modern cereal box in a sea of vintage ones: A box of Millville Gluten-Free Cocoa Rice.
Fireworks sales were not legal in Indiana until 2006. The closest state in which fireworks sales were legal in the 1980s would have been in Tennessee.
Modern Cheez-It boxes can be seen from behind on the top shelf as the kids are exiting the Big Buy store.