Gadget Hackwrench, from Chip and Dale’s Rescue Rangers.
Many of the folks others are mentioning, I found attractive, but I think that Gadget was the only full-on crush.
Talk of New Zoo Review is tickling my memory neurons— there was a live-action kid’s show right around the same time period as NZR that I think was on Saturday or Sunday mornings. It involved a group of youngsters ( teens or early 20’s ) who hung out at a beach having adventures or something. One of the female characters I swear was in a bikini every episode, all episode long. She was the only reason I watched the show. Anybody remember the show I’m referring to?
Markie Post on Night Court and Allysa Milano or Who’s the Boss
Monty Python’s Carol Cleveland, um, BY A LONGSHOT. As Arthur Peauty’s wife, or lip-syncing Cleese while vamping away on a bed, or getting groped by Brian Equator, or as a travel agent’s assistant wanting to go upstairs, CC was always setting the bar for tv hotties for this little’un.
The quite eye-openingly hot Gloria, Felix’s ex-wife in The Odd Couple, Janice Hansen. Always had my radar out for her, but saddened to never see her materialize in anything much more.
Dayum Julie London from Emergency!
(already syndicated by the time I saw…)
Yvonne DeCarlo (Munsters) and Carolyn Jones (Addams Family)
Julie Newmar, Lee Meriwether or Eartha Kitt? I assume you were over 12 when Michelle Pfeiffer had her turn, and I won’t even mention the Halle Berry trainwreck…
Oh God, yes!
While I learned to appreciate Eartha Kitt’s charms later on, Catwoman was always Julie Newmar for me back then.
Thanks largely to the costume department on the 60’s Batman series, Newmar and Yvonne Craig (Batgirl) were many a young boy’s first taste of what puberty was going to feel like.
Lee Meriwether for me.
Looking back upon it, I really didn’t appreciate curves until I was well into puberty, which I hit rather late in hindsight.
At age twelve and under, the only crush I recall was Mary Ann on GI.
Of course, I realized there were lots of pretty women on TV and I appreciated them, but Mary Ann was the only one I was really hooked on.
One possible rival: Ann Marie on That Girl, just because I had a girlfriend in 5th and 6th grade who resembled her.
Honorable mentions:
Carol Post
Samantha Stephens
Honey West
Elly May Clampett
Betty Jo Bradley
Catwoman (Julie Newmar)
Morticia Addams
David Hartman (The Bold Ones: the Doctors segment), Good Morning America
Very attractive Toon.
Dianne Kay from “Eight Is Enough.”
https://images.app.goo.gl/78Mn6a2xn1VtwZna9
I was so in love with Lt Uhura! Beautiful and techno-competent, smart, just a little sassy, and so self-confident (okay, when she wasn’t being scared. I never really believed those scenes. “Captain, I’m scared.” Who are you and what did you do with the real Lt. Uhura?)
That was mine at age 5 or so. Probably during first run, but even then it got repeated over and over. I knew there was something different about her - wasn’t old enough to figure out what it was thought.
For those of you who had a crush on Marcia Brady, and those of you who had a crush on Martha Quinn, how did you react when Martha Quinn became a Brady?
Yeoman Rand–something about that blonde bee-hive.
Lisa Gerritsen from, “My World and Welcome to It,” and, later, “Mary Tyler Moore/Phyllis.”
Oh, God! How could I have forgotten Joi “Mrs Superman” Lansing? I was enamored of her long before I ever even heard of Mary Ann! 
Wow, she was indeed quite lovely!
Looking through her credits, I think the only thing I ever saw her on was an episode of The Beverly Hillbillies in which Lester Flatt and Earl Scruggs visit the Clampetts, and despite each having a gorgeous wife, they’re both still pining over the one that got away - Jed’s cousin Pearl. Joi played Lester’s wife.
Sad to see she passed at only 43.
Get out of my mind!
(but you forgot Elizabeth Montgomery!)
I egregiously forgot Suzanne Pleshette in The Bob Newhart Show.
Season one really stood out, in that it was way more lax - compared to the remaining seasons - with SP in surprisingly scant negligee in bedroom scenes. It seemed like each episode she was being showcased in either a short teddy, or long, diaphonous robe, or form-fitting nightgown with open, ruffly cleavage.
Quite galvanizing for a kid. But then in successive seasons I was bummed to see her more conservatively attired. 