A FORMER WASHINGTON REDSKINS CHEERLEADER'S MEDICAL MYSTERY TURNED HER INTO AN INTERNET SENSATION - BUT IS HER ILLNESS FOR REAL? -- ON ABC NEWS' "20/20," FRIDAY, JULY 23

Plus: Would You Give Your Child Medical Marijuana? And: Online Buyers Beware� Fake Designer Shoes

Washington Redskins Cheerleader Ambassador Desiree Jennings, 25, had everything going for her until one day her body suddenly stopped working, turning into a twisted, jerky mess. For some inexplicable reason, when she runs, Desiree's body untwists and straightens out, and sometimes she can walk backwards and sideways without trouble. Footage of this unusual phenomenon spread quickly online, making her an internet sensation. Was it caused by a flu shot, as Desiree thought? Her journey for answers to this medical mystery takes her to a controversial osteopath in North Carolina and ultimately leads people to question whether or not her affliction is real. Jim Avila's report airs on "20/20," FRIDAY, JULY 23 (10:00-11:00 p.m., ET) on the ABC Television Network.

And: Kids are constantly being told to "just say no" to drugs. So why would a mother give her 12-year-old marijuana? Although there are several well-documented beneficial effects of using marijuana for medicinal purposes -- including helping to ease nausea, stimulating hunger in chemotherapy and AIDS patients, and providing general pain relief for a wide range of symptoms -- there are no studies done to show the effects marijuana may have on the developing mind. Even so, some parents are turning to medical marijuana as a way to help their children who are plagued with psychiatric disorders ranging from Autism and OCD to even ADHD. This new course of treatment has ignited a debate and raised the question: Would you give your child medical marijuana? Chris Connelly reports.

Plus: Buyers beware! In an age where billions of dollars are spent online on shoes each year, the counterfeit market has picked up on the trend. Fake Christian Louboutin and other top designer shoes are being sold for hundreds of dollars online as the real deal -- even though they're fake replicas from China. How can you keep from being duped into buying a fake, and how easy is it for counterfeiters to obtain the merchandise? Deborah Roberts reports.

"20/20" is anchored by Elizabeth Vargas and Chris Cuomo. David Sloan is executive producer.