The earliest source I can find for it is in the Weekly World News, a satirical sibling to the National Enquirer that published blatantly outlandish stories from 1979 to 2007. Recurring topics were UFO encounters, religious miracles, cryptozoology (bigfoot, yetis, Bat Boy, etc.), celebrity scandals, and health and diet fads. The specific headline "I married Bigfoot" was first mentioned in Volume 16, Issue 19, published on February 7th, 1995.