I just (re)installed IP the other day after playing with just the base game on my new computer. Of course IP is buggy and I knew it wouldn't be perfect. But I'm having issues with mermaids. They aren'...
Well so far, so good. I used MC Cheats (is it weird that it sounds like a DJ name? "MC Cheats coming at ya with some sick beats!") and turned all 4 mermaids human and then mermaid again, at City Hall. And then used MC again to invite one of them over, and she has scales! I'm hoping to send my sim scuba diving and we'll see if he finds any mermaids.
I thought there were more than 4 in the game, but that's all that MC showed.