Biography
Even a Stopped Clock is right twice a day.
A character who's normally Book Dumb and/or The Ditz comes up with a valuable insight. The character most often heard belittling their intelligence sighs heavily and concedes, "I Can't Believe I'm Saying This, but I agree with him." (Often adding, "And that scares me to death.")
This can often be the result of pure chance; a wild guess turning out to be true, or Right for the Wrong Reasons. In other cases, this is because the dumbass isn't willing to rule out an option due to thinking it illogical at first, or lacks knowledge of something that would limit more intelligent characters' thinking and cause them to rule out the correct idea. Or sometimes, more intelligent characters are overthinking it and the simple guy is the only one to think of Stating the Simple Solution (especially if it involves Cutting the Knot).
Also heard when two people of more or less equal intelligence, who normally disagree about everything on ideological grounds, find that there's one opinion they share. In other cases, the character with a valuable insight may be of a little less moral standing — in which case, this trope then becomes somewhat of an inversion of Your Approval Fills Me with Shame.
Truth in Television, and can be seen between Vitriolic Best Buds and Internet-nemeses on Message Boards.
Compare Actually Pretty Funny, Too Dumb to Fool, The Cuckoolander Was Right, Wisdom from the Gutter, Mistaken for Profound, I Have Nothing to Say to That, Nobody's That Dumb, and The Dissenter Is Always Right. When the character is the subject of this reaction because they're mean, unlikable, or evil, it's Jerkass Has a Point (or Villain Has a Point when it's coming from an outright antagonist). If the reaction stems from the character making the point having a knack for doing the opposite thing, it's Hypocrite Has a Point. When the author intends to make a character's argument come across as wrong, but the readers agree, it's Strawman Has a Point. Not to be confused with Obfuscating Stupidity, where a character is only pretending to be stupid, though too many moments like this can make people suspicious of such a character (and will sometimes lead to Epileptic Trees amongst fans about characters who are actually stupid secretly being that trope).