>>57452444I've twice thought of fic concepts for this, but never followed through. It was either going to be (A) your typical bodyswap trope story, set during the OS (likely early on, during Indigo League), with Serena becoming OS Ash and having to keep her/his cover with Misty and Brock while Ash had to go through the miserable grind of being subject to 4am Rhyhorn racing practice in Serena's body, or (B) like your pic, a super silly short concept of Serena literally just taking Ash's place, dressed in his OS clothes and all.
