I have something.
Prove that I am not the single, sentient being and the rest of you are figments of my dream world.
Define prove?
Demonstrate the truth or existence of (something) by evidence or argument
Solipsism? What a pointless exercise when your hypothesis neither makes a single meaningful prediction nor is it falsifiable.
Notwithstanding the normal human foibles (cultural/racial chauvinisms, inaccurate records, general ignorance, etc) we all agree on the universe around us. We share it. Grass, green; sky, blue; gravity, 9.81 m/s2; and on and on and on. It has an incredibly long lived history shared between countless independent entities (stars, galaxies, nebulae,
Kimberella, Lucy, etc.) that all agree that the universe exists. Is it possible that it all popped into existence last tuesday, perfectly set up to look old? Yep. Is it possible if the entire universe is in your head, a single night's dream? Sure. Is there any difference between them and a normal reality? Not a bit. Nada. There is nothing in that question to test, nothing to prove, no new knowledge to obtain.