Really quite sad that you chose to focus on a scientifically discredited personality test here. MBTI is popular in business and industry circles mostly through courses and consultants who are more interested in telling a good story and providing anecdotal results than actual, large scale, positive change. This is not to say that it's useless for character building, but it's much more akin to D&D alignments than actual personality: no real person is Lawful Good or Chaotic Neutral, but they're useful for sketching out character traits quickly. However, you spend the majority of this video explaining the system and not once noting that for describing actual people, it's entirely useless, due to the already mentioned inconsistency in retakes and lack of a bimodal distribution in its traits.
I studied this test in school and it really, really, really does not work.
All of us have a natural ability to create characters in our minds because it's what we do every day of our lives. Think about it, you can never really know another person, all you can know of them is the mental image you've created of them through the information you've gathered. We see this in how people can jump to totally wrong conclusions based on some news headline, for example: Lone Gunman Defends Commuters from Armed Robbers on Subway. You hear that and you immediately begin to create a story in your mind about the lone gunman, a story that might end up completely shattered when you later hear more details about what a nutter said lone gunman is in his personal life. Still, the ability to flesh out characters is there and we use it without even thinking. The worse thing you can do when trying to get young creators to understand character building is to give them rules that distance them from this innate process. Researching these cheesy personality tests, or indeed even reading too much Tv Tropes, inhibits good writing. They're something to get past, not something to start from.
This goes back to the episode on writing convincing female characters. You need to start from a place of thinking of your characters as actual people (even if they're giant amorphous aliens from deep space who sense the world through many worm-like appendages). Every person may well be governed by an ever fluctuating set of rules but you discover these rules by watching what characters do, not by deciding what they're going to do based on a chart. The best way to find out about a character is to spend a lot of time with them doing a lot of writing.
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All of us have a natural ability to create characters in our minds because it's what we do every day of our lives. Think about it, you can never really know another person, all you can know of them is the mental image you've created of them through the information you've gathered. We see this in how people can jump to totally wrong conclusions based on some news headline, for example: Lone Gunman Defends Commuters from Armed Robbers on Subway. You hear that and you immediately begin to create a story in your mind about the lone gunman, a story that might end up completely shattered when you later hear more details about what a nutter said lone gunman is in his personal life. Still, the ability to flesh out characters is there and we use it without even thinking. The worse thing you can do when trying to get young creators to understand character building is to give them rules that distance them from this innate process. Researching these cheesy personality tests, or indeed even reading too much Tv Tropes, inhibits good writing. They're something to get past, not something to start from.
This goes back to the episode on writing convincing female characters. You need to start from a place of thinking of your characters as actual people (even if they're giant amorphous aliens from deep space who sense the world through many worm-like appendages). Every person may well be governed by an ever fluctuating set of rules but you discover these rules by watching what characters do, not by deciding what they're going to do based on a chart. The best way to find out about a character is to spend a lot of time with them doing a lot of writing.