Einstein Hair

You should keep it. Looks more science-y.

—The Eleventh Doctor to Albert Einstein, Doctor Who, "Death Is the Only Answer"

It seems that to properly convey that your male character is an Absent-Minded Professor or a Mad Scientist in fiction, you only need one thing: give him Einstein-esque hair. Bonus points if you go for the complete look. Additional bonus points if he uses a Van de Graaff generator or a Tesla coil instead of combing.

And it actually makes sense given that:

Albert Einstein was both an Absent-Minded Professor and a scientist (mad or not, it is open to interpretation).
He is one of the most (if not the most) famous scientist in history.
His hairstyle was really... idiosyncratic.

Contrast Wild Hair, which also indicates indifference to society's opinion, but otherwise has quite different connotations. Sub-Trope of Messy Hair. Compare Labcoat of Science and Medicine. See also Memetic Hair, which this style can be an example of.

Examples of Einstein Hair include:

Anime and Manga

Leo Shishioh in GaoGaiGar has this.
Dr. Agasa of Detective Conan.
Desty Nova has a better groomed than usual version of this in Gunnm.
Dragon Ball: Despite not being a scientist, the old man Alternate #17 kills at the end of the Androids arc, or almost kills on the anime, is a perfect example of this.
Dr. Schroeder from Darker than Black has a curlier variation of this. He's a Mad Scientist doing fundamental research in PANDORA.
Professor O'Reilly in Rocket Girls has gray hair in this style.

Film

Star Wars: Yoda once you get over the fact that he's green. In fact, his character design was partially inspired by Einstein (and bits of Gandhi and LDS President Spencer W. Kimball) to evoke the "benevolent, wise old man" archetype.
Doc Brown from Back to The Future.
- He even comments on the fact that he still has the hairstyle when watching a video of his future self.
- Christopher Lloyd said in an interview that the hairstyle was inspired by a combination of Einstein and Leopold Stokowski (the orchestral conductor in Fantasia)
In the second Scooby Doo Movie, while messing with some potions, Scooby gains great intelligence, guess who grows a white "mane" as a side effect?
Prof Jacob Barnhardt in The Day the Earth Stood Still (1951), who's clearly an Einstein Captain Ersatz.
Larry of The Three Stooges had a similar haircut, making it a rare example of the hairstyle being applied to an imbecile.
Gene Wilder pulls this look in Young Frankenstein.
Mac from Chicken Run manages to have this, despite not actually having hair.
Rotwang, the Mad Scientist from Metropolis.
Sherlock Holmes, as played by Robert Downey Jr., has this type of hair.
Wheeljack from Transformers: Dark of the Moon has wiring on his head that gives him this appearance.

Live-Action TV

Dr. Forrester from Mystery Science Theater 3000.
Firefly: When Shepherd Book doesn't have his hair tied up, it looks kinda like this. The sight was freaky enough to send River screaming for cover in the episode "Jaynestown". Granted, he is not a scientist but a priest...
Charlie Epps in Numb3rs tends to have this sort of hair.
In the Doctor Who mini-episode "Death Is the Only Answer", it turns out that the Doctor gave Albert the idea once a time travel experiment-gone-wrong made his hair frizzy.

Music

Ludwig Van Beethoven
Edvard Grieg (In the Hall of the Mountain King) looked like a combination of Einstein and Twain, and his hair sure reflected it.

Theatre

Non-mad scientist example: Cirque Du Soleil acrobat/clown Brian Dewhurst often styles his naturally gray hair this way as part of his onstage look -- Nouvelle Experience, Mystere, etc. In the former show, he played an elegant but eccentric chamberlain from a Magical Land; in the latter he plays a Screwy Squirrel.

Video Games

Dr. Wily of Mega Man, not to mention the fact that his first name is Albert, making him practically an evil Expy of Einstein. Nobody's quite sure why Capcom made the villain so clearly Einsteinian, but a popular (half)joke theory is that it's some lingering anger over the Atomic Bomb.
Doctor Zelinsky of Command and Conquer: Red Alert 3.
- Einstein himself showed up in the first two Red Alerts.
Potential resident Dr. F ("The F stands for ROBOTS!") of My Sims.
Nicolai from Space Colony.
One of the stock NPC scientists in Half Life looked like Einstein.
The original Civilization represented scientists with Einstein-like figures wearing a lab coat and having their hair a mess.
Dr. Pettrovich Madnar in Metal Gear and Metal Gear 2.
- Madnar's portrait in MG 2 was actually a digitalization of Einstein's. Then again, Snake was Mel Gibson...
The Invisible to Normals therapist NPC in The Sims 2.
The Science booster pack in City of Heroes includes 'Mad Science' hair which is pure Einstein.
Ripper Roo has one in Crash Bandicoot 2: Cortex Strikes Back to go with his higher education studies.
Team Fortress 2: An Einstein-esque wig was part of Medic's costume for the 2011 Halloween event.
Kalrow from Asura's Wrath has this type of hair.

Web Comics

Dr. Germahn from El Goonish Shive.
Uncle Otto in General Protection Fault.
Dr. Zweistein from The FAN.
Bob and George's Dr. Wiley Lampshaded
In Girl Genius, Agatha has some hair sticking out upwards the top of her head. According to Word of God, that's because a Mad Scientist must have mussy hair, so basically it's the long-haired female version of this trope.

Web Original

Doctor Horribles Sing Along Blog: Mild example with the titular Doctor Horrible, whose hair is messier in his villainous identity than as Billy.
The Whateley Universe mutant codenamed Cheese (yes, he picked it himself), who is described with hair like this already, even though he is a teenaged supervillain.

Western Animation

Parodied in a Sidney Harris cartoon, where such a scientist is walking down a corridor and his colleagues remark (paraphrased) "His theories aren't going so well, so instead he's working on his resemblance to Einstein."
Dr. Weird in Aqua Teen Hunger Force.
Dr. Scratchensniff from Animaniacs used to have Einstein Hair, but he tore it off bit by bit in frustration during his first sessions with the Warners.
Inverted in Captain Simian and The Space Monkeys, where The Smart Guy Dr. Splitz has slicked back hair, but his dimwitted alternate personality Splitzy has wild Einstein-like hair.
Technus' first look in Danny Phantom had this with a slight mix of Frankenstein's bride.
Flint in Cloudy with a Chance of Meatballs has such hair.
In Scooby Doo and the Cyber Chase, the gang visit a college friend who is working for a professor who not only has the hair but every other physical characteristic of Einstein as well.
In the educational talking dog cartoon, Martha Speaks, a scientist/doctor with Einstein hair explains in the opening that a regular dog can gain the ability to speak by eating alphabet soup.
Dr. Two Brains from the cartoon Word Girl.
In an episode of Tiny Toon Adventures, Plucky Duck convinces Shirley to use her psychic powers so he can channel the spirit of Einstein and pass a test. He gets the hair, the 'stache, the accent, an oversize head...but doesn't get any intelligence and flunks.

Other Media

One of the variant versions of Clippy the Microsoft Office Assistant is a Chibi version of Einstein.

Real Life

Mark Twain actually had this hairstyle before Einstein did, making it Older Than They Think.
Tim Burton, anyone?^[context?]
If you're into physics, you've probably seen at least one professor like this.
- Ditto computer science, especially programmers involved in free and open source software.
Old people in general tend to get that Einstein look.