The finale of “WandaVision” premiered Friday, bringing to an end a successful season for Disney+’s first Marvel Studios series — and with it, a parallel drama that has been unfolding on TikTok. For weeks, fans have taken to the short-form video app to theorize about the show’s many mysteries, creating countless videos of themselves talking, singing and making memes about the show.The finale of “WandaVision” premiered Friday, bringing to an end a successful season for Disney+’s first Marvel Studios series — and with it, a parallel drama that has been unfolding on TikTok. For weeks, fans have taken to the short-form video app to theorize about the show’s many mysteries, creating countless videos of themselves talking, singing and making memes about the show.