What is the film technique where you see a person while things around it are moving fast?

How would I be able to do something like this (equipment, programs, camera)? Some examples are in Garden State, some Scrubs episodes, and Accepted. To elaborate, a main character is standing in the middle of a busy street and everyone passing by moves very fast while the character remains at normal speed.

What is the film technique where you see a person while things around it are moving fast?
It's known as a key in in television. In older days a weather person would stand in front of a surface such as a screen which was an olive color. In the video switcher, they would have all the graphics that would appear over anything that was that color. You would not see it in the studio as the weather person pointed to places on the map. They would watch a monitor and move their hand to different places. In movies and most video such as a dude standing with a crowd moving by. We used Untramax where backgrounds are pool chalk blue. Another running video of crowds and traffic, cliff shots and scenec backgrounds are added to the mix

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