This creeped me out! I saw a sim come out of the bookstore holding an invisible toddler, and placing them on the ground. I went to talk with this sim and could hear the baby giggles out of nowhere, somewhere close but there was no babies anywhere... Anyway, the guy turned out to be a nice fella and a single too, so my sim and he proceeded to have a date. After it I went back to the park and no nooboo sounds anywhere, so they decide to go steady. Next day, the guy shows up at my sims lot holding a not-so-invisible baby girl.
Turns out this guy is the first ever single townie father of two I've ever seen in my game (who knew they would have babies without a relationship). I would say my sim was tricked into a relationship, heehee, but who would mind as she has the family oriented trait.