Leo McCluskey, medical director of the ALS Center at the University of Pennsylvania, told Scientific American that Hawking's case has highlighted how variable the disorder is.
"On average people live two to three years after diagnosis. But that means that half the people live longer, and there are people who live for a long, long time," McCluskey said. He went on to explain that with ALS, the most common cause of death is either respiratory failure, as motor neurons run the diaphragm, or malnutrition and dehydration, as swallowing muscles deteriorate.
"If you don't have these two things, you could potentially live for a long time – even though you're getting worse," he said. "What's happened to him is just astounding. He's certainly an outlier."
Mathis also suggests that photos of Stephen Hawking on the Internet are "conveniently not dated" and Hawking appears to have gotten more youthful as time has gone on. On the other hand, he bafflingly compares photos taken decades ago of the professor with more recent ones, pointing out that he had dark brown hair when he was younger and "now he is gray", proving conclusively they are different people. Astonishing stuff.
Other "evidence" points to photos from Hawking's wedding to Elaine Mason in 1995. Mathis shows two pictures in which her dress looks slightly different (most likely due to lighting) and claims that it's evidence that the photos have been re-staged using the imposter Hawking, to erase visual evidence of the first Hawking ever having existed.
Weirder still, conspiracy theorists appear to think that the replacement Hawking does not have ALS by suggesting the "new" Hawking does not have hands that have been curled by the condition. They believe he is a man who has for the last 30 years pretended to be paralyzed in an attempt to cover up Stephen Hawking's death, rather than, you know, Stephen Hawking.
Which is all, of course, nonsense.