Just need a quick answer.

I crossed my eyes while playing a 3DS and the world ended.

I don't really understand what you're saying, so I'm just going to say no. 

" I crossed my eyes while playing a 3DS and the world ended. "

It seems like its doing the eye crossing for you. So yeah pretty much.

I'll just take the soup.

Nobody here knows how it works.

It's basically two screens posing as one. The slider on the side dictates the angle at which the screens are pointed.

You mean like those pictures where you kinda cross your eyes and a 3D image appears? I can't remember what they called those books, but I could never do it.
 
3 minutes later: I think they were called Magic Eye books...

No. You don't have to do anything to your eyes, it just works. You don't know how.

No, You cross your eyes, you still see one image but with eyes crossed. 3DS has two screens and through magic its those two screens that is key to making stuff 3D, otherwise we would be playing our PS3 and 360 games in 3d already if we could just willingly always cross our eyes. 

You guys be joshin' me! 
 
So what I'm asking is if the 3DS stereoscopy ( THREE-DEE) is the same as the crossing your eyes trick. Basically, the 3DS is crossing its 'eyes' for you and that's how the 3D works. 
Right? I'm wondering if its like that, cos that's the only way I can think it can work without glasses.

I'm not sure how it works exactly but a guess would be that it renders each scene from slightly different angles and then will show scene A, refresh to scene B, refresh to scene A, refresh to scene B etc... showing each scene 30 times during the 60hz I imagine the screens refresh rate to be. Thus making it work like our eyes do normally without crossing them. We can see depth because we have two eyes viewing from lightly different angles, close one eye and you lose depth.  
 
Really I don't know how it works this is just a guess. 

Nobody here knows how it works.