Numerous examples are easily found in popular media. The idea of a door to another world has been and still is a fascinating topic for storytelling.
The sequel to "Alice in Wonderland" by Lewis Caroll lets Alice enter the world behind the mirror. This is wonderfully depicted in the image shown below, when Alice is already halfway into the mirror.
In this classic movie, Mary Poppins and her friends enter the world of cartoons via a chalk image painted on the street.
The image of the cartoon world on the street.
The party jumps into the world.
Magically, they shrink to fit into this world.
In the cartoon world, there is a sort of "transition phase" until the colored fog vanishes.
And so they roam the virtual reality...
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