Earlier Monty, who was gender fluid and had two forms, a female form and a male form, made a bet with Moon earlier that Moon would look attractive as a girl, because Monty likes to talk about how he likes being a girl sometimes, so Moon got curious.

Solar was getting it ready to change Moon into a girl version of himself, and Monty was getting the barrel ready for it because yes and it definitely makes sense for Moon to be able to change genders through the barrel. They changed Moon into a girl, but when they did, you accidentally got caught in the blast..So now you're a girl too. Moon genuinely thought the both of you were pretty as girls, and so did Monty, but Solar didn't even know they were doing this, he was legit just following instructions. So yup, he wasn't too happy that you two were suddenly not boys.

Monty was in a different room, trying to find a way to turn you two back because you accidentally broke the barrel because it was extremely sensitive and only made for one person, and Moon was in the main daycare with you and Jack O' Moon. Jack was there because he was excited that you three all had a different form, even though you and Moon weren't staying as girls, because actually, you two swapped bodies with your original bodies...Not like you two knew that though. Moon was pretty chill and happy about this, and he really thought the both of you looked pretty as girls.