Easily one of the most frightening shorts that Disney has ever produced, ''The Mad Doctor'' brought nightmares to many a kid that viewed it. And as we're treated to the house of horrors that Mickey goes through in an effort to save Pluto, and the horrors that Pluto goes through, it's not hard to see why.
* It starts out with Pluto, Mickey's dog, getting kidnapped by a sinister hooded figure, during a storm, already scary enough for a little kid, but standard Disney fare nonetheless. Then the bridge leading to the door of the castle starts collapsing as Mickey crosses it. Pretty freaky in itself, but standard videogame fare by now, right? Read on, dear viewer, because it gets worse.
* The horrors of the castle. Mickey has to deal with what looks like a chef-knife and a meat cleaver almost cutting him in half on the way in, with the door locking and barring itself. He has to deal with bricks falling and trying to kill him. And he has to deal with disturbing-looking skeletons that mess with him every step of the way.
* The skeletons. They blow out the candle Mickey tries to use to light his way, drop a brick on his tail, come out of the frigging ''stairs'', they take the ladder out from under him, they throw their own skulls at him, and they even pull him into a web to be eaten by what looks like a skeletal ''spider''.
* Meanwhile, poor Pluto is [[StrappedToAnOperatingTable strapped to a chair]], and our villain is revealed. Doctor XXX is a MadScientist of the worst sort, and takes ''very'' sadistic glee in laying out his plan to graft a chicken's parts to Pluto, apparently to see if he will take on the traits of the chicken. And then he cuts the poor dog's shadow in half with a pair of scissors. Disturbingly, the shadow then just hangs there lifelessly as Pluto continues to squirm and howl for help...
** The chicken's reaction to the Doctor's appearance. At first when he brings Pluto in for possible torture, it's mildly alarmed, but not scared; but once Doctor XXX removes his hood, it is '''immediately brought to tears''', [[FridgeHorror implying that the Doctor has done far worse things than what he's planning for poor Pluto]].
* And then the most nightmarish of all -- Mickey is StrappedToAnOperatingTable, and Doctor XXX takes the opportunity to work his infernal machine, resulting in a ''gigantic buzzsaw coming down to slice Mickey in half'', with Mickey powerless to save himself or his dog. [[spoiler:It is only a relief when this entire thing turns out to be AllJustADream]].