When scientists get obsessed with their research to the point that they neglect their grooming, health, family, and/or human ethics, they are called “mad scientists.” I suppose it’s because it’s easy to lose yourself in a problem.
“Characteristically, I think it’s ENTP that falls into the mad scientist category.

Even one of the most beloved anime characters (ENTP) calls himself literally a mad scientist but actually it’s the INTJ girl of the “lab” who actually creates things like time machines, etc.

But conceptually, I guess INTPs have a lot of potential to become mad scientists, but not behaving like an intelligent version of the Joker.

INTPs admire “chaos” and chaos? Well, it’s the main concept behind being a mad scientist.

I’m sure you already know how intelligent and creative INTPs can be, but there are two major obstacles that won’t let them fall into the dark side of science that easily:

They are the worst type of procrastinators you can ever find and they are 99.99% of the time unmotivated. Unlike any normal person, you can’t motivate them to do something for fun, the only thing that makes an INTP actually do something is a serious deadline.
There’s a tiny little cognitive function in an INTP’s stack which is called Fe and it tends to keep the harmony. So, now, if an INTP becomes a mad scientist and wants to burn the world in chaos (look it’s really cool if you ask me and if any of you wants to do that, be my guest), it means that they have lost their small amount of awareness over their Fe. It also means the INTP starts to grow more and more childish and after a short amount of time, there’ll be a significant distance between them and their maturity.
Tl;dr If you want to see a guy acting like a mad scientist without actually being one, ask an ENTP. If you want an actual mad scientist (which doesn’t act like one), go brain wash an INTP so they can stay motivated and give them an ISTx assistant”