I think someone already said Angela Cartwright.
Oh, and Susan Dey from The Partridge Family:
Both of Dempsey and Makepeace.
Mostly, the shows I liked as kid have stood the test of time (even the A-Team has in a way, because I always knew it was fun trash), but I rewatched this show once and was mortified. I’ve rarely seen anything so bad in my life. But I loved it as a kid, and really loved both of them.
ThisHayley Mills? I had a big crush on her as a kid - which was good for me, as she’s in some critically-aclaimed films as well as fun Disney stuff. I have an acquaintance who looks very much like her, and I’m sure she’s weirded out by me staring at her. Not that I fancy her any more, but the resemblance is just so uncanny.
I loved Hayley Mills in The Moonspinners.
James Mason as Captain Nemo in 20,000 Leagues Under the Sea, seen at age 10 at a kiddie matinee in the early '70’s. I attribute my life-long love of beards to him.
I’ve posted this before, but I was in love with Peter Pan from the Disney movie since as long as I can remember. I was also in love with the cartoon version of Robin from Batman.
My first sexual attraction was toward Doc Holliday as played by Val Kilmer in “Tombstone.”
After I got over Jordan Knight, I ran across Val Kilmer in “Willow.” How you doin’, Madmartigan?
I first had some curious stirrings watching David Bowie in Labyrinth.
The weird in me started early. 
I think it might have been more his voice than his tights, though. And my first age-appropriate celebrity crush was Atreyu, too.
Oh, I don’t know… the tights were pretty hot.
My first big crush was Flint McCullough, the scout on Wagon Train. He’s not my type anymore, but I adored him, and I adored Appaloosa horses for his sake.
I had a cheap pot metal heart with my first name etched on the front. I got it at the local fair. I used to write his name on the back so it would be close to MY heart as I wore it.
I had it BAD. That was 4th or 5th grade, I guess. Then The Man from Uncle came on, and I forgot Flint in favor of Illya Kuryakin (David McCallum.) Who still looks pretty good, btw. 
In the spirit of full disclosure, at the risk that I’ll never be able to live it down, I’m pretty sure that my first celebrity crush wasthis little guy.* In retrospect, I can see that he had many fine qualities to his credit – that he was courageous, smart, a strong swimmer, socially and sexually unthreatening** to little girls like myself (for sure, he never used harsh language and he wasn’t “grabby”), always saved the day in a heroic way, and, with his gorgeous eyes and wide, toothy grin, was as cute as the Dickens. I don’t remember all that much of what I thought and felt towards him in that formative period of my life, except for wanting to be able to jump in the water and join him for a swim… and hug him and kiss him and probably ride on his back for a few laps. :dubious: A true devotee to his cult, I caught his show on daytime reruns and wore his T-shirt throughout my toilet training period***… and FWIW, I’ve admired swimmers ever since. 
But moving on a bit, a few years later I had my first real (or at least species-appropriate) crush – for Rudolph Mantooth, co-star of Emergency!. Come to think about it, the paramedic heroes of that show were basically the walking bipedal equivalents of Flipper, although the 'Tooth had great hair when he let it grow long… and a toothy grin, appropriately enough.
- I suppose it could’ve been worse. Comix artist Robert Crumb went public years ago with the nugget that he had had a childhood sexual obsession with Bugs Bunny, or at least Bugs when he was in drag. (The Wagnerian music probably helped.)
** Although there is something very Id-like and priapic about a playful dolphin, don’t you think? Hmm, come to think about it, I never did go through a pony/horse phase like most other girls did…
*** As family photos attest, I wore that tiny T-shirt a lot, until it was more raggedy than my Raggedy Ann doll. A tender mercy indeed, that most of us don’t really remember our toilet training.
One of the earliest would have been the middle daughter on Petticoat Junction, I remember being jealous when she got married on the show. Also around that time, Maryanne from **Gilligan’s Island **and Agent 99 from Get Smart. Later on Laurie Partridge and Marcia Brady.
They were both mammals, but their friends warned them it would never work. Interspecies romances: next on Geraldo.
Two young crushes (I’m talking about five) that I remembered from a work conversation last week:
Susan Richardson of “Eight Is Enough” fame. So that’s where I got my lifelong love of redheads!
And this has to be the most obscure. Remember the 80s kid’s science program on PBS, “321 Contact”? They had a segment on teenage detectives called the Bloodhound Gang and I loved the lead detective Vicki. I just found out her name was Nan-Lynn Nelson. Here’s an episode here.
David Yost as Billy the blue power ranger when I was like 7. My friends used to tease me, but then I was vindicated in high school when they all admitted they had crushes on him too. I still think he was pretty smokin’.
I also thought Bill Nye was cute in a geeky sort of way. Again, still do.
Kristy McNichol.
When I was six, I loved Davy Jones. I ran into him in person about twenty years later, and it was both disappointing and embarrassing.
Zombie Threads rise from the grave on Halloween.
Aw! Mine was the pink one! But I liked her better as Suzie Q.
Even after I got older, it broke my heart when I found out she absolutely hated being a Power Ranger. Your guy has been five different ones, and even came back for one of the newer series.
The earliest one I can remember is Lara Jill Miller from Gimme a Break.