Multiple Dimensions and Extraterrestrials: My thoughts

Today I came across this article about two experiments looking into the fourth spacial dimension. Essentially they found what looked like a cross-section of a four-dimensional object. As we all know, a cross section of a three-dimensional object, like a cube, results in a two-dimensional shape, a square. It follows, then, that a cross section of a four-dimensional object would have only three dimensions.

Now, how do extraterrestrial beings come into play? This is where it becomes complicated, if it isn't already. Imagine a two-dimensional person, let's say Mario back when games were much simpler and existed in two dimensions. If I were to somehow pass through his world, which is thinner than paper, he would see a cross-section of me, and this odd shape in the sky would change as I moved. In our three-dimensional world, however, if an alien who existed in four dimensions were to pass through, we would see strange three-dimensional objects in the sky. Personally, this is how I explain UFOs without simply dismissing them.

Now this is the mind-blowing part: there is mathematical, though to my knowledge not experimental, evidence of possibly nine different dimensions. If something were to live in all nine, how would they be able to interact with our world? Would they even be able to see it? I'm not a scientist, so I don't pretend to have the answers. All of this is theoretical, but interesting nonetheless, to me at least.