I know I'll take heat for this, but when I see kids doing this, it just bugs the heck out of me. As Dad tells him... we are in a Squatchy area... and there are a lot of them in CO... and yes son you've got a Squatch print... yadda yadda yadda. The kid is too old for the Easter Bunny, he's too old for Bigfoot tales AS FACT. There, I said it.
"Some people think so, Son. What do you think? Why? What else could this be? What other signs can we find? Why is that a sign of BF instead of another animal? What animals live around here? Let's find their tracks." etc Help your child to think, not push an undocumented creature on him as fact. Let him be curious and explore and test out his own thoughts, give him room and a little guidance and good resources.
There's no accounting for how parents raise kids. Some teach their children to be themselves, some to be what they would have them be, and still other would make them into copies of themselves. Sadly, there are no requirements in order to have children other than to have functional glands.