Last Thursdayism is the belief that the universe was created, last Thursday.
It doesn't have any actual followers or rituals but proving it wrong, is impossible.
Not because the universe actually did pop into existence last Thursday, but because Last Thursdayism is falsifiable.
It can not be shown false. Any evidence that you bring up against can be explained as a part of the everything that was created last Thursday.

Many people believe that for a theory or explanation to be scientific, it must be possible to refeud it or to prove it wrong. So instead, last Thursdayism falls into the domain of philosophy. Where luckily there are razors, little rules of thumb that help shave of unlikely explanations. The most famous, Occam's Razor. When faced with a choice between two explanations choose the one that requires the fewest assumptions. Occam's razor can shave off Last Thursdayism because it requires fewer assumptions.

One of my most favorite razors cuts of so much stuff, it's not even called a razor.
It's called Newton's Flaming Laser Sword.
It states that if something can not be settled by experiment, then it is not worthy of debate.