Contrasting with the Genius Ditz, who, while usually foolish, has one area (or some) in which they are absolutely brilliant, we have the inversion: the Ditzy Genius, a character who, while they are very intelligent and talented in several or many areas, has absolutely nothing in the way of common sense, logic, wit, or tact, or at least isn't good enough in those areas.
This can occasionally be shown as naïveté to the point of stupidity, and/or nigh-Suicidal Overconfidence/inability to see the danger or flaws in what they're doing. In any case, these characters end up landing themselves in trouble more often than not. They are capable of doing pretty much anything they put their mind to, but they also tend to forget to ask themselves if they should do it, or even question themselves on why they even do it in the first place.
The primary difference between a Ditzy Genius and a Genius Ditz is that a Ditzy Genius has high general intelligence but is highly inept at something more mundane than their intellectual interests (social skills, for example) or lacks common sense, whereas the Genius Ditz usually seems dumb or clueless but is in fact highly proficient in at least one fairly specialized skill or field of knowledge. Contrast also Book Dumb, which is a character smart in mundane life but abysmal in everything academic.
In any Tabletop RPG using The Six Stats, this kind of character-type will have high Intelligence, but low Wisdom.
Sometimes, this is a deliberate characterization decision made to give a highly intelligent character a Fatal Flaw, or make them come across as weird, or any number of other reasons. Other times, it happens entirely by accident because the writers keep tossing the Idiot Ball to a character who's (perhaps only because we're told as much) supposed to be academically brilliant.
This trope is Older Than Feudalism — one of the earliest instances of this trope dates back to ancient Greece, more specifically from Plato's dialogue Theaetetus, in which Socrates explains that philosophers were back then often perceived as absent-minded because they didn't care about such mundane things such as gossip or social fads, but instead about truly important matters such as the essence of knowledge.
Compare Nerds Are Naïve, though note that not all nerds and geeks are geniuses and vice versa. See also Cloudcuckoolander or Brilliant, but Lazy, especially in cases when the character's intelligence is largely informed. One of the standard Hollywood interpretations of a nerd, along with Extraverted Nerd. Very closely related to Smarter Than You Look and Bunny-Ears Lawyer. Also compare Absent-Minded Professor, who isn't foolish so much as forgetful. See also No Social Skills and Sacrificed Basic Skill for Awesome Training. If the character's deficiencies are in the areas of manners or consideration for other people, see Insufferable Genius.
