If you have not already viewed the Web’s present favourite train phenomenon, do yourself a prefer and watch “Prancercise: A Fitness Exercise.” It is worth every minute.Joanna Rohrback’s YouTube video, uploaded on Christmas Day closing 12 months, change into a sensation this week, topping 2 million views as of late as bewildered viewers passed the video on to each other. Used to be the thin girl within the salmon cardigan …