Ashley enjoys dancing. Mary-Kate's the tomboy. Ashley's the shopper. Because they're so popular with pre-teens, the Olsen twins have the clout to do anything they want. Videos they make are guaranteed sellers.
Television shows they appear on get a healthy bump in the ratings.
So, a new series starring both seemed like a no-brainer. That doesn't necessarily qualify as acting. But the two believe they're on the right track for a lifelong career. Now, they're even at a point where they feel comfortable giving advice. You can do it again if you mess up.