la menor
When a guy sees a little girl with big tits and a big butt, but she's still a kid. He thinks she's older than she really is.
I saw la menor at the mall. She was wearing a bra and a skirt, but she was still in 3rd grade.
My friend hit on la menor. He thought she was 18, but she was still in 2nd grade.
That girl at the park was la menor. She looked like a woman, but she was still in 5th grade.