Most Helpful Guy
it's about how you act, more than what you wear.
Just laugh a lot and act very happy and silly, I am 23 and I have a friend who's like this, she acts like she's 12 even tho she is 23, she just posts silly videos of her self doing silly stuff and she laughs at anything, and gets mad easly, but she wears normal. she also always share stuff about cartoons she loved like Ariel the mermaid, Cinderella, lion King she keeps in touch with her childhood favorites. that's how she seem very very young.
Most Helpful Girl
Wear brighter clothes, use natural looking make-up -also create the illusion of your eyes being bigger with mascara & eyelash curler, do NOT use black eye-pencil on the lower part of the eyes-, make the annoying baby voice.