Board Thread:General Discussion/@comment-30388913-20161101185429/@comment-23979190-20161119011026

"More Logical" answer

Fun Girl may or may not be Megami Saikou's sister because in her dialect it said "She'll never know she had a sister." She also said her dad only had one invention, but in this universe he has many. Megami and her ALSO say lines that are Undertale references.

"You're going to have a bad time." - Megami

"Shattered across space and time." - Fun Girl. Also a female Gaster on her page.