It's a bit weird. It doesn't always happen, BUT if you do the "Hang out with friends" event, or any other date/event with someone with a sizable pink bar, your Sim suddenly becomes the most popular Sim on the planet & you'll end up drawing 5 or more other Sims, into your conversation. If you're not "With" someone, then no one wants to talk to you.
As for the Sim possession issue. One time, I even tried to save, then restore my game & my Sim just kept walking around the map, until it was out of his system.