Les Franken (Michael Rapaport) is a parking meter attendant who wants to do something useful with his life, so with that in mind has applied to be a test subject for a new line of medication. He is seen by Dr Dobson (Jack Kehler) who gets him to sign the requisite form - including a disclaimer that he will keep all talk of the drug secret - then is offered a bottle of blue pills to take, one with every meal, though Les is so keen that he swallows one immediately, curious to see what effect it will have. It is meant to lift an self-doubt in the patient, but what Les finds are side effects...
Side effects in his mind, that is, in what increasingly begins to look like an allegory of mental illness from writers and directors Hal Haberman and Jeremy Passmore in this, their debut. Even though it took that tack, this remained one of many superhero movies to emerge in the twenty-first century that were less than convinced of the merits of dressing up in a costume to fight crime with your newfound powers. Kick-Ass was the biggest hit in that vein, but there were others such as the superior Super and comparable Defendor, but in light of this the negatives of adopting an alter ego to combat the bad guys affected the more traditional efforts as well.
Special had the bonus of being one of the first, so they could say they were at the start of the trend, or they would have if something like Blankman hadn't been around some time before, but where rubbish superheroes had formerly been part of the comedy genre as much as anything else, Special was rather more serious. Not that there weren't any amusing moments, but it was not really aimed at the funny bone, as you were meant to see past its protagonist's obvious failings and perceive the damaged nobility he contained, which the new medication had brought out. Trouble was, he thinks that he is gaining incredible powers as in the comic books he likes to read.
But we see, and everyone else can see, that he's deluded thanks to the chemicals messing with his mind, so he can't really float or run through walls or read people's thoughts, that's all in his imagination, though incredibly convincing to him as he experiences it, dismissing his injuries he begins to receive as the effects of his exertion. As in many of this ilk, Les (presumably given the Franken surname as an allusion to Frankenstein), sees it as his duty to bring down any evildoer he sees, which begins rationally enough in contrast to how he ends up when he tackles a convenience store robber. But then he graduates, if that's the word, to jumping anyone he thinks looks suspicious, which leaves a load of people battered and bruised and the police taking an interest.