Well, If they really wanted to; they could say Patrick forgot who his real parents were. It has happened before.
Honestly, I don’t think they really want to explain anything continuity related, spin-off or otherwise. The way they explained Sandy in Kamp Koral seemed less “joke’s on you, we planned this from the start” and more “ugh, fine. we’ll put this in so you guys will stop whining”.
Especially since, officially speaking, nothing is canon. They’ve made it clear that consistency has never been a priority, full stop.