You forgot Dana Sterling, who combines much of the best of the three.
When I was in the Middle School set, Holly, from Land Of The Lost was the apple of my eye.
And, of course, Morticia.
Not from a show but definitely on TV, back in the 60s-early 70s Joey Heatherton had to be just about every boy’s idea of a perfect sleeper.
And which cigar brand was it that had the babes, Dutch Masters or White Owl?
Mark Paul Gosselaar, who has aged really well apparently. Jonathan Taylor Thomas. Rider Strong and Will Friedel.
And a somewhat more embarrassing TV crush, Mr. Lucas. (He is the second from the left.)
Agent 99 from Get Smart - Barbara Feldon — YOWZAA!!!
I Dream of Jeannie - Barbara Eden
Penny, from Lost in ASpace
Billie Jo, Betty Jo, and Bobbie Joe - Petticoat Junction
Catwoman from Batman (Julie Neumar, I think)
oops. Forgot Susan Dey, Karen Valetine and Maryann.
I didn’t forget anything. Dana doesn’t do anything for me. I mean, look at her hair!
Nobody has mentioned Thomas Magnum yet? I never have lost my crush on that guy!
Slightly Off Topic. I had a massive crush on Shannon Miller during the [whichever] Olympics.
My first crush was on the Professor from Gilligan’s Island.
Then quick flings with David Banner, George “Gonzo” Alonzo, and Ponch.
Apparently I like 'em short. 
Sailor Mercury! That’s right, a cartoon character. I’m just that cool. I stopped watching much TV when I got “older,” so I’m not sure who else I crushed on.
Oh my Og! I wasn’t going to mention this, seeing as how I was pre-grade school and all, but my heart back then belonged to Gilligan. Which, you know, was kind of geek beatnik hot during “Dobie Gillis.” Plus, overall his sense of humor kicked ass.
As to more ‘realistic’ crushes, I had a major, major, MAJOR thing for Shaun Cassidy when he was on “The Hardy Boys.” Then there was Danny (Carlo Imperato) from the series “Fame.” I’m sure there were others, since some have already been listed here, but I’m having a brain fart remembering them.
Another vote for Bailey Quarters! (Next to her, I never could get the appeal of Jennifer Marlowe/Loni Anderson.)
Annette for me. At seven years old, I knew that for some reason I wanted to go to bed with her, but I had no idea why. I think my breast sensors were working early.
Ronja Rövardotter. And Martina, the little girl singing in this video. I looked it up because of this thread, not having seen it in over twenty years. The attraction, oddly enough, has faded in the interim.
