Paedophile effect
It's when someone looks like they just walked out of a candy store, but they're really a grown-up trying to get you to think they're still a kid. They're hot, but they're also trying to trick you into thinking they're still in grade school.
My neighbor's daughter is 21 but still wears pastel colors and acts like she's in middle school.
My friend's crush is a guy who still wears a backpack and claims to be 15, but he's 26.
My teacher's kid is 18 and still wears a fanny pack like it's the 90s.