I didn't know what you were talking about in particular, though I'd heard of the special garments, so I Googled "Mormon magic underwear". First hit (and many of the subsequent ones are on that site) was http://www.mormonmagicunderwear.com/ , which is NOT a mockery site but trying to explain it.
(no subject)
Date: 2012-03-22 08:45 pm (UTC)Lower hits were... lower.