Woah, hahaha, that is awesome! Reminds of the time my sim (they're infuriating sometimes) left her toddler at the park.
I didn't know until later when I got a message saying that (Keellee) was out after curfew.
I switched to her and she was "finding Michelle." I followed her outside my house. She didn't go in. Just sat there. Her mother didn't even freak, it seems that's a common occurence in the sim-universe.
Speaking of which, have you ever tried aging Grim?
I have seen him in the park, and he talks to people, but the only way I could interact with him (besides being mean, and I'm not dumb enough to anger the Grim Reaper) was if I invited him to join conversation with someone else.
Even then, I couldn't address him directly, so I settled at making Jokes. (We're BFs now, though the communication barrier is still there)
He behaves the same as Casey when I try to age him though even though he has the trigger age transition thingie when you click on him.
I'm curious!