Here are some theories that are IMPOSSIBLE to prove or disprove as of now :3
--Warning: CONFUSING--

-You are living in a virtual reality of a computer of the future

-Nothing is real, and/or everybody else is fake and you are the only "real" one

-Everybody sees colors differently (e.g. My blue is what you see as red although we both call it "blue")

-The universe is infinite, therefore somewhere else something/body is doing the exact same thing as you but a tiny tiny bit differently

-The existence of life outside Earth

Comment what you think about these! <3