My daughter tried to defraud the tooth fairy. We wrote a note to them for my son explaining he had lost his tooth, he may have swallowed it. She thought this was a good plan and wrote her own letter. We think as a joke as my oldest had told her none of the supernatural stalker characters exist...
My oldest is autistic and fiercely logical. Aged 6 ish he worked out the truth. The worst part though was he told my younger too who were smart enough to believe him. Always made me sad that they missed out on the whole thing so young.
Such is life in a neuro diverse household though.