In this one or two minute film, a farmer sets up a tent with a screen and an old movie projector that he runs by turning a crank. He has some friends and family there to watch. The movie he shows features a big old-fashioned train moving toward the viewers. “It’s coming right for us!” One those watching yells, and in his panic, knocks over a lantern that hits an ear of corn that starts popping and gives the farmer the idea for popcorn.
Can anyone find a link for this?
In googling the term you are looking for is " Pre-Show Bumpers" . There are dozens of collections of these with many popcorn and soda ads on youtube.