A Smith called Pete offers a movie that shows the audience the new 3-D process, in which one wear goggles, one colored red, and one green to provide a three-dimensional image.
It wasn't new, since experiments in the process had been going on for decades, and a lot of test footage was made in the 1920s. Like other technical advances, it lay unused for decades, save for the occasional short like this, until the 1950s, when it was seen as a possible answer to the decline in film attendance engendered by television.
That didn't last long, but occasional revivals of the process happen every decade or two. In the meantime, this offers some nice use of the process.