Mad scientists come in many varieties.
In my case, I operated an area called the Science Shed at the Science Museum of Minnesota. Kids would come by, singly and in groups, and I'd show them all sorts of neat things. I had a Van de Graaff generator to make their hair stand up, a laser beam (which, among other things, showed some of the neatest patterns when you put a diamond ring under it). There was an oscilloscope to show them their voiceprint, a metal detector, all kinds of things. One was a blacklight which made peculiar things glow in the dark - including, sometimes, false teeth. But I couldn't count on false teeth being present in the Shed at any particular time, nor on their owner being willing. So when I needed a crown on one of my front teeth, I asked the dentist to make one that glowed. He said that since blacklights had become common, the dental supply companies had fixed that problem; but he looked around and found some old supplies. So now one'a my Two Front Teeth glows under UV illumination. The kids loved it.
This is known as throwing yourself into your work. It also helps give an air of eccentricity, which was a professional asset in that job.
Then, we have Captain Mercaptan. He's a mad scientist, originally from the fragrance and cosmetics industry. How does such a thing make for an effective super(villain?). There's a story behind that.
Perhaps the strangest I've encountered, however, was the Mad Architect. He was mad in the very nicest way, of course. It happened while we were in Hawaii.
A banyan tree wants to be a forest. It sends down little twisted vines from its branches that thicken and take root and become more trunks that send out branches, and so on and so on. We stopped at a secondhand store in Hawi, where the proprieter told us to drive towards Puhola, look for a phone booth and a hostel, and take the next left (a dirt lane). Down a path behind the church, he said, was the most wonderful banyan tree he'd ever seen.
There was a splendid banyan in the church yard, but they kept cutting off those stem-root things so it couldn't send down more trunks. Beyond the church was a path, leading into a real jungle. And in the jungle there it was, a one-tree forest, the greatest banyan of all. It had a date palm growing up its middle. It had thick trunks supporting mighty limbs. It was wonderful.
The path continued, so we followed it, and found a mad architect named Shawn. He lived in an expansive bamboo and blue-plastic tent, large and comfortable. His bathtub was outside, under a tree. He had a pet chicken, a Rhode Island Red by its color, that broke his artworks and pooped on him in his bed when he didn't rise early enough to feed it.
Shawn designs geodesic domes to be built in bamboo, the only material, he says, there is enough of for everyone.