Of the ones who actually engage in it, Robbie would have been the slowest to get used to the idea. The Foster family are practicing nudists, so that came easily to them. Mark and Mandi took to it very quickly after that fateful trip to the secluded beach with their mom. Suzy and Sally are pretty much precociousness personified and they're ready to lose their clothing at the drop of a hat (or a pair of panties). Robbie, on the other hand, took some convincing from Mark and Mandi before giving it a try, and even then it was super late at night when the risk of being seen was at its lowest.

Not my favorite video game series, but I remember enjoying EarthBound when I played it. Have not played either Mother 1 or 3, though.