P6S-221 was a planet in the Pegasus galaxy which held a Stargate as well as a local population. The locals thought that if they wore hats it would keep the Wraith away and so, when the First Atlantis Reconnaissance Team visited the planet sometime before they discovered a giant Quantum Mirror, Teyla Emmagan was happy to humor the people and wear a hat, along with the rest of the team. (ATL: "Entanglement")