The earliest crush I remember is on a cartoon character and in typical fashion (considering my heritage), who could it be other than princess Jasmine from Aladdin?
Paulina Porizkova I convinced my dad to take me to see the movie "Her Alibi" and told him it had to be good because Tom Selleck was in it but really I just wanted to see Paulina on the big screen. I don't think my dad ever forgave me for that one. Christine "Moose" from "You can't do that on television", Firestar from the Spiderman cartoon , Jaclyn Smith from Charlies Angels and Maureen McCormack "Marsha Brady" are close runners up for early crushes.
I admired a lot of cool male characters as a kid but didn't actually have a crush on any characters/actors until I was probably about 12, at which time I developed some solid crushes on Harrison Ford and Noah Wyle.
Jessica Alba in Flipper, yes Before Dark Angel. But that migt not count as "Celebraty" as ahe was not yet famous.
Mine was easily Maureen O'Hara. Specifically in the film The Quiet Man during the first few years of my life. And then I watched the Charles Laughton version of Hunchback and she was even better then I thought. Those films microwaved my adolescence.