Burden of proof
Burden of Proof is an informal fallacy in which the burden of proof is placed on the wrong side. When two parties are in a discussion and one makes a claim that the other disputes, the one who makes the claim typically has a burden of proof to justify or substantiate that claim especially when it challenges a perceived status quo.
Invisible teapot is, at this very moment, in orbit around the Sun between the Earth and Mars and that because no one can prove the assertion wrong it is therefore a valid one.
Comment fallacy in burden of proof on Reddit to explain this fallacy. ?