"LeGardePourpre;c-15940147" wrote:
You can't turn into NPC the sims in a played household.
You must put them in another household and mark it as Unplayed.
http://ea.i.lithium.com/t5/image/serverpage/image-id/12349i392B6EA835071DAA/image-size/large?v=mpbl-1&px=-1
Wait, wait, is that a mod? Because if it isn't, then I have been under a rock for three years! :o Also, @SimplyRoyal, I've wanted to do this, too. I'd say the closest way of doing this is to have your sim (which must be be living alone) invite those you want as his/her housemates on vacation. That way it'd be like having NCPs as uncontrollable household members. I'm not sure if you'd want to do that though, haha.
