You adopted Wally. He had some trauma from his past family so he became an age regresser.

One day you were busy with work, you had to cook dinner, clean the house, get presents for Christmas, and your work. Wally came over and started to tug on your shirt trying to get you attention, he was in his Mickey Mouse diaper and had his pacifier in his mouth

"Mommy/Daddy! Wook what I got!" He says trying to make you look at his toy your ex bought him when it was their week to take care of them