What does "that" mean from "It’s that"? And is it okay just to say "I'm" instead of "It's that guy"?

Rebecca

At a very basic level, "that" is like pointing verbally at something in order to focus another person's attention on it in particular. In the case of the video, it is probably being used to sound very casual and friendly. I agree with you that you could simply change "it's that" to "I'm" without having any impact on the meaning of the sentence. Ex: I want that one on the top shelf. Ex: Isn't that that guy from school?