I had never heard of the "Hollow Earth Theory" until you just mentioned it. I just checked out
the Wikipedia article about it and it has a pretty interesting back story.
I just spent way too much time looking for this cartoon I saw as a kid at my local museum about a kid who decided to dig to the center of the Earth. It was pretty goofy, but it he started with a shovel and ended up upgrading to this submarine with a drill on it.
Anyhow... ever since that video I've believed in the narrative about the crust and all of the different layers down to the core.
All that said... I'm personally a fan of the Hollowhttps://en.wikipedia.org/wiki/Hollow_Moon"]Hollow Moon Theory[/URL]. :D I'm not saying I think the moon is hollow but that's one I've heard of before and found it interesting. The whole Reptilians using it for mind control thing... I don't think that's the case, but that's the one I liked. :)