It's easy to see why this movie is a classic, but that's not the same as being a great movie that holds up years later.
One only needs to think about this in context to understand how shocking it must have been during its time: remember this predates _Blood Feast_, and _Night of the Living Dead_. We have some surprising moments of gore at the end, which again, pretty bold, considering. On top of that, we get some nudity - va-va-voom!
_The Brain that Wouldn't Die_ undoubtedly inspired several movies, the two most notable being _The Man with Two Brains_, and _Frankenhooker_.
So, let's break down the story - there's not much of one, so it won't take long: a doctor's fiancee is decapitated in a car wreck. Said doctor wants to attach her head to a new body. Monstrum ex machina. The end.
There are actually some moments of good camera work here, but the entire production is so inconsistent. Whether it's the writing, the blocking or the acting, any good moments are promptly undermined in the next scene. There are long stretches without dialog, that just feel incomplete or just lazy.
Let's go back for a moment. The movie starts with our doctor (Bill) is being told by his - soon to be bodiless - fiancee (Jan) that she is super excited to be his wife - remember that. Moments later Bill is driving like a maniac - which if a reason was established fir this, I never heard it - that leads to a crash, resulting in Jan being decapitated. Bill uses 1960s science (read: magic) to keep her head alive. Oh, Bill also has an Igor (or Fritz, if you prefer), Kurt - more on him later. This is where the movie starts to go off the rails. Bill just becomes a creepy narcissist, who wants to find the perfect body for Jan's head; no real development here, just deal with it. Running parallel, Jan has fully jumped onboard the crazy train, like fucking choo-choo! She was so ready to marry this guy, now she's angry because he... kept her alive? Isn't that what doctors do? Her issue is that she doesn't have a body - look, I get that this is a sci-fi/horror movie, but there still has to be some internal logic rooting the motivation, otherwise, what are we doing here? If she had been clinically dead, and was then revived only to wake without legs, would there still be a problem? I don't want to get into philosophy here, but you can see where I'm going. Anyway, Doc Bill is body hunting, so he begins where you do... the strip club. Classy guy. This goes nowhere, but it does have some of the worst ground fighting I have ever seen, and we also get a catfight joke. Meow.
Billy boy eventually finds his way to a nude model (Peggy) who is a radical feminist - in other words, one guy was cruel to her, ergo she hates all men (her words, not mine). Man, she would fit in perfectly in 2023. Anyway, I agree with Bilbo that she would be great if not for that damn head. While all of this is happening, Jan has become aware of a living experiment in a locked room next to her. Said experiment is able to attack Kurt by way of a smaller door of the one that is locked. Then the monster rips Kurt's arm off! It's here I have to question the physics of how this happened. Like, draw me a diagram. Furthermore, how is he able to rip a man's arm off - we're talking gorilla-levels of strength - but can't bust down a door? Until it's convenient, of course. Ultimately, the monster kills Bill - whoa - saves Peggy, and Jan burns alive.
Despite its many flaws, I am happy I watched this. Clearly ahead (no pun intended) of its time, and with just a few tweaks, it could have been an 8/10. Must watch for all fans of horror, sci-fi, or just campy cult classics.