Watch the father's lips when his kid talks. I don't know what is going on here, but Mediaite offers three explanations:
1. That the boy has a earphone in and his dad is telling what to say and, for some reason, thinks he’s a much better ventriloquist than he actually is.
2. That Hudson’s responses were all scripted and Hinckley can’t help but mouth his brilliant dialogue.
3. Hudson is actually some kind of AI-style android that is being controlled by its “father.”
Either way, this video is absolutely insane
A fourth possibility is that the dad is nervous about what his son is going to say, and he is echoing the kid's replies, in a sort of Clever Hans kind way. Please offer up other possibilities in the comments.