Here's another submission I originally posted on Reddit.
Honestly, I think a whole video could be created to cover all the secrets from all three Earthbound games but in this post, I'm just going to cover the whole Giygas-is-a-fetus-Ness-and-crew-are-trying-to-abort theory.
In Earthbound, aka Mother 2, Giygas is the universal cosmic destroyer hellbent on destroying earth... or something. In order to stop him, Ness and the gang must defeat him when he's at his weakest... so they travel to the past to confront him.
They make it to the past, enter the cave Giygas is hiding out in, and take him out. But it's hard to tell what you're fighting when you finally find him. At first, it seems like you're fighting some kind of organic machine, which Pokey calls the "Devil's Machine." You see what appears to be Ness's face poking out. Maybe Giygas is on the verge of being created in Ness's image though how he knows what Ness looks like is beyond me. (I guess MENTAL POWERS.) Shortly after, Pokey turns off the machine and sets Giygas free, but he looks like an indescribable, wavy mess. Personally, by this point, I think you're fighting some kind of multi-dimensional blob of pure psychokinetic energy.
If Giygas is actually a fetus that Ness is trying to "abort," then there has to be some visual proof. Well, the cave they enter sorta looks like a vagina.
Inside that cave is where Ness finds the Devil's Machine:
It looks like a cervix.
When Pokey sets Giygas free, Giygas looks like a distorted mess. But if you look closely, you'll see the outline of a fetus.
I don't think you're fighting a real, actual fetus by this point. I think the image is just there as a subliminal message, kinda like something Stanley Kubrick would do in his films.
Or maybe it's some kind of space fetus.