Pyrostrata wrote:But the most perplexing thing of all to me was why was I, a GIRL, attracted to an obviously male-targeted toy/comic/cartoon (I bet many of the lady-fans have asked that very same question!)?
Pfft, that's easy. For one, boy stuff is cool because it's not all cutesied/trendied up to the point of saccharine overdose/lameness. Far too many marketers seem to think that stuff being pitched to girls must be pink and fluffy or "hip and trendy" (or sometimes both, for maximum pukeage).
For two, boy stuff usually has mostly male characters, which equals at least a few cute guys. (OK, so that doesn't quite apply here specifically, the scarier variety of TF fangirls notwithstanding...)

On a more serious note, a couple major factors for me personally:
One, TF has a pretty unique depiction of giant robots. Consider, most portrayals of robots in fiction tend towards one of the following:
- Piloted mecha. Gundam, Voltron, Robotech, etc.
- Servants of some sort, whether in the Asimovian "Three Laws of Robotics" vein, or tangenitally inspired by such a la Robbie, B-9, Marvin, C3PO and R2-D2, etc.
- Singular robotic characters in the mold of Data from Star Trek, one-off creations trying to become "real boys". Then there's the Replicants, which are a combination of this and the previous concept.
- Bad guys trying to kill off humanity. Think the Cylons, Daleks, etc.
But TF's concept of an entire robotic species with individual personalities, varied non-android bodies, complex moralities, etc.... I'm actually having trouble thinking of any other fiction that's really done that, outside of the movie Robots or maybe Futurama might qualify. I'm sure there's gotta be *something* else, but it's not coming to mind at the moment. In any case, I find the idea rather fascinating.
Added into this is the whole concept of transforming. Aside from being a great toy gimmick, it adds a new twist to the "aliens among us" trope. Except now instead of being your boss, next-door neighbor, or potential girlfriend, they're your car, tape deck, or that jet that up until a little switchover flew over your house regularly *without* shooting at it. Doesn't it now suck to be you.

Two, characters! I am a big character junkie, and the TF mythos is like being handed a whole ton of character candy.

There are no real "red shirts" in the sense of disposable, nameless characters... thanks to the tech specs, even minor/obscure characters usually have some kind of developed personality. Among the ones who do get more screentime, there's enough focus episodes and varied interactions between all of them to make life interesting. Finally, there's so many characters that you're bound to find at least one that suits your "favorite character" tastes. (Which makes me wonder why thinking up original TFs is so popular... I know that for any given character idea I've been able to think up there's almost always an existing one that fits. But that's another tangent.)
Those are the things I can think of off the top of my head. Maybe more later when I ponder it further.