pedocrush
When someone "has a crush" on someone younger/thinks someone younger than thenselves is hot - this is not the typical 50-year-old man likes 5-year-old girl thing. The word can be used when somebody fancies someone some years younger or when a grown-up or just older person fancies a child star in a movie etc. 
"Omg, I totally have a pedocrush on that kid from Charlie and the Chocolate factory!"

"I know he is only 16, but I totally have a pedocrush on him!"