While your uncle went off to get the equipment to "cure" you from your french maid transformation, the girl he'd said was your cousin came over with a playful grin.
"So you chose to put on a slutty little maid costume?"
"Pardon mademoiselle. I've always been like zis," you answer, a bit confused.
"Well, how can we make you 'always have been' even cuter...? Ah, perfect!" She selects a cat girl outfit and just takes the ears and tail butt plug. "Here, wear this." It is not in your nature to dissobey, so you let her place the ears on your head. As soon as she does, the cat ears attach and become part of your head. And they've always been part of you. Your whole body shrinks a little bit as normally the entire cat outfit would have shrunk you into a house cat. But strange things happen when costumes are combined. You just look younger.
"Turn around and bend over with your knees straight," she orders, now standing talker than you despite your heals. You blush and turn around obediently. Bending over lifts your frilly mini skirt, revealing your panties. You struggle to keep still as your panties are slid down, exposing your butthole and pussy.
Lubing up the rather thick butt plugg, your cousin shoves it inside you, eliciting a small mew of protest from your lips. The cat tail poking out of you twitches and comes alive. Your cousin watches how it slowly moved up to your tailbone and attaches, as the plug vanishes. But you can still feel it big and thick inside you.
Your body regresses even more. You're now just an adorable little cat girl maid, blushing wildly and moaning with every step you take, as it makes the butt plug shift inside you and tease you. It's like Schrodinger's cat now. The buttplugg both exists and doesn't exist. You can feel it there, but you can never remove it. Your ass is forever filled, yet anyone could still easily fuck it.
"Okay, I found my staff. Now if we hurry, I think I might be able to reverce the costume's spell on..." Your returning uncle stops dead in his tracks when he sees you as a young little cat girl maid.
"Oh god. What have you done!? You've entangled multiple transformations together."
"I just thought he'd look even cuter as a little cat girl," your cousin says. You can't help yourself but pull up your hands in a cat paw pose, tilt your head playfully and say, "Nya." You didn't know what they're talking about. You've always been like this.