But... they're displaying something. Some odd effect of heat on the display tube? But wouldn't the heat cause a compromise somewhere in the glass that would break the vacuum preventing this type of display?

... and who disposes of TV's like this anyway? Probably some crazy dictator. (3rd image on page, darn website image protection. disclaimer: image from Indiana Jones, I do not support the opinions expressed within)

[Edit: fixed link because it would only show the image from the containing page]
[Edit: generalized to "compromise" for clarity]