Tinfoil or tin hats is a term that
orginated from comes from people wearing [http://en.wikipedia.org/wiki/Tin_Foil_Hat tinfoil hats] to keep out the "alien signals" and is generally used to describe the super paranoid or conspiracy freaks.
In [[RPS]] fandoms, a fan is said to be wearing a " tinfoil hats" or engaging in "tinhattery" when they are convinced they are being sent secret signs that their boys are really IN LOVE and DOING IT.
If used in relation to self e.g. ''I am putting on my tin hat'' , it is used to indicate that the author realizes the preposterousness of what they are saying but are happily indulging in their RPS fantasies.