Closed Captioning: More Ingenious than You Know

A VCR isn't like most other forms of visual recording media where it takes an image and records it in some other format to be converted back to an image later, it's actually a 1-to-1 analogue recording of the broadcast signal (minus any degradation from being an analogue copy). So by design it includes any tricks they used to include metadata in the normal broadcast signal. The mechanics of how they worked are actually pretty interesting, I highly recommend Technology Connections' video on the subject [1], as well as the one on closed-captioning [2] (and his series on analogue TV in general [3]) [1] link [2] ▶ this video [3] link