A non-critical minor character whose sole purpose is to make things harder for the Hero(es) to achieve their goal and cause complications along the way. There is no way to educate, negotiate with or otherwise talk sense to a [[SelfPropelledBarrierOfStupidity SPBofS]], and this is apparent to the audience from the moment they appear. This is often the abusive sibling or baby sitter. Can also be an [[ObstructiveBureaucrat uncaring government bureaucrat]], the StupidBoss, or the school principal (when not a key character in the story). A [[SelfPropelledBarrierOfStupidity SPBofS]] need not be in a defined position of authority over the protagonist. Unlike TheMillstone, the [[SelfPropelledBarrierOfStupidity SPBofS]] is an outside obstacle, rather than a member of the protagonist's adventure troupe who inadvertently screws things up. Also, TheMillstone is usually a more developed and well-rounded figure, with a backstory, etc.
[[folder: Film ]]
* The colossally ignorant older brother in ''Film/WeirdScience''.
* Dr. Fredrick Chilton in ''SilenceOfTheLambs''. In many ways, he's the tool's tool - actively confounding the crime-solving efforts of Agent Starling and working toward his own demise at the hands of Dr. Lecter. Although Chilton's death does not arrive by the end of the movie, it's so close we can almost taste it.
* In basically every movie where some scientist main character comes up with evidence that a disaster is imminent, those people who ardently refuse to believe him. Often a CommanderContrarian who is [[KarmicDeath likely to cause his/her own death]].
* In Action films, this will be the FBI if the protagonists are local cops, local cops if the protagonists are FBI, or both if the protagonist is independent of either two groups (if either one isn't the BigBad or working for them, that is).
[[folder: Literature ]]
* [[ForgottenRealms Ed Greenwood]] is fond of using these as guards in his novels. No matter which protagonist (or group thereof) encounters them, unless they're personally known to these stalwarts they will try to run the 'interlopers' off, arrest them, or kill them outright...anything ''but'' check whether they might have actual legitimate business that requires them to move past.
[[folder: Live Action TV ]]
* In the 1970s ''DoctorWho'' serial "The Silurians", UNIT and the Doctor have to deal with Dr. Lawrence, director of a nuclear power project. The man refuses to accept that there is anything more happening than possible sabotage and equipment problems, even as people die or suffer nervous breakdowns around him.