So, this started becoming a concern for me while playing as my main sim. He's a merman, and my original idea was for him to be very close to the sea, to the point where I could choose to keep him in the water if I wanted to. He's a simple guy that loves music and the ocean, and this led him to become a three-star celebrity. Eventually, I just completed the world famous celebrity aspiration for the satisfaction points before opting out of fame. Anyways, he started to get abducted nightly when he reached above level 10 for the musician career branch. On this play through, after a rags to riches style challenge, he has level 10 logic and I completed the Nerd Brain Aspiration. So, he's got a rocket ship. For this sim, I don't want him to get alien pregnant, and I might sell the rocket ship to avoid that.
I don't mind the abductions because it keeps things interesting after reaching max level. However, I've started to max out the household specifically to avoid him coming home pregnant. Merfolk still have the dried scales bug, and I imagine the hybrids could still be buggy. I'm not even a fan of hybrids, to be honest.
Anyways, I still thought it was funny that aliens wanted to keep abducting merman musical genius at the top of the musician career branch. I didn't even have a rocket ship or intentional interactions with aliens at the time.