@stuebinm It's an allusion, made by @pigworker, to the film “Goodbye, Lenin” which concerns a patriotic/civic-minded woman in East Germany who fell into a coma just before the fall of the Berlin Wall, and then how when she wakes up her son tries to protect her from the shock by creating fake news reels and so on that perpetuate the illusion that the DDR had kept on going.

In the context of proof assistants, what it refers to is that you may evaluate some terms at one point in time, and in doing so produce closures that capture the state of knowledge at the time they were frozen, and if you are not careful to "refresh" old things against the current state (which may have new solutions to various problems) you can run into trouble.