"Mama Mia! What's a baby doing in my research? Well, never mind that. Whose baby do you think this is, Gnawty?"
"Beats me. Hey, how about we take care of it, at least until it's older!"
"That's a great idea!"
"Oh, I want to be the mom!"
"I don't think you can be the mom, Gnawty, since you never wear a shirt.
"You're right. If I was a mom,
Just call me Daddy!"
And so, Luigi and Gnawty switched gender roles for some reason, and took care of Jr., AKA the baby. After a beautiful stroll through town, the park, and the town's park, the lovely couple then...