@SqueamishNerd , I did a little testing on Goofball Sims and Childish Sims and this is what I found so far:
Childish Sims could:
play with doll house
play with small toys
play, hug, and talk to large stuffed animals
play in the bathtub
They cannot use the Voidcritter battle station or packs, the monkey bars, the puppet theater, use the kid's doctor kit (for empathy), or the kid's chemistry table
Goofball Sims could not do any of these activities, even the ones that Childish Sims can do!
There might be more things that Childish Sims can do, but these were what I could think of at the moment! 😇
Update: Childish Sims can play with small toys, but you have to take them out of the toybox first , as you can't direct them to do so from the toybox itself.😉
