Infantiles have an endearing childlike playfulness to them that is charming to some people, this I'm guessing is also different in men and women, women would be more girly and men would be boyish.

Immediately what comes to mind is Mozart in Amadeus or a character like Tony Stark or Sherlok Holmes (Robert Downey Jr.) or the photo of albert einstein with his tongue out. They have a sort of easy going, non-chalant attitude.