Starlight
On the first image, a Triangle-person is shown beneath a starry sky. The caption says: “Look at the sky - there is something hidden in plain sight.”
Then they are shown looking at the space between the stars: “What do you not see? It’s not pure starlight!”
Then a diagram is shown. The Triangle-person is blinded by light-rays coming from many stars, stretching into the infinity. A sky sphere is depicted, with stars projected on it. The sky is 100% occupied by starlight. Caption says “If the universe was infinite, it should be!”
Another diagram is shown, with significantly less stars, and a dashed line depicting the “limit” of the universe. The Triangle-person is no longer blinded and they are showing how things are limited with their hands. Caption: “But it’s not. Why? Universe must be limited in some way: in space, or time…”
Final image depicts an alien saucer holding up a cloth with stars sewn on. It’s says “Just doing my laundry”, while the Triangle-person seems annoyed. Caption: “…or someone is blocking the view!”
The conundrum of why the sky is dark (or not 100% filled with bright starlight) is known as Olbers’ paradox, but I did come up with it by myself too, which allows me to claim a bit of the fame. Thank you.
The specific reasoning is this - if the universe existed for infinite amount of time, and is infinitely big, then whichever direction we look, we should encounter a star. So the sky should be uniformly bright with starlight, possibly all blazing like the Sun. Since it’s not, then there must be some limits in play.
It could be time limit - starlight only had so much time to do the traveling in since the birth of the universe, so not all starlight had a chance to reach us. It could be the distance - universe is of limited size and there isn’t a star in every direction. Or there could be something blocking the view - such as cosmic dust (it’s quite sparse but it adds up across large distances).
We also can’t exclude the possibility we are enclosed in a cosmic terrarium, playthings of aliens who are on a different scale, or just enormously powerful.