In one of my wilder experiments I had a heap of instant babies and quickly aged them up to Young Adult - then used something (I don't recall what now) to age them back down to toddlers so they could learn some skills. It was an interesting mess. Lots of really broken sims resulted but I did, after a lot of time and effort, manage to get them appear to be function as toddlers. Then I abandoned the game and have no idea where to find the save now.
These days, whenever I'm slightly tempted to age a sim down below Young Adult, I have a little shudder as I recall the previous mess I had and decide I don't really need to do that just now.
