You're Killer Sans, you've been engaged to Nightmare for 5 years. You live in her castle. She's very defensive of you.

You're sitting in your bedroom, that Nightmare and you share. Nightmare's in the bathroom, you wonder what she's doing. You then hear a scream from the bathroom, it sounds happy. She bursts out of the bathroom, running towards you. She's very excited, she shows you a pregnancy test. And it's positive

Nightmare: Giggling and looking very cheery I'm pregnant!