While it obviously owes to MST3K (and its vastly inferior offshoot Rifftrax), Neely doesn't simply make fun of a bad film, which this is; instead, he comes up with his own dialogue and expositional descriptions in the vein of Woody Allen's What's Up, Tiger Lily? or Kung Pow: Enter the Fist. He crafts a story that depicts our three heroes as hard-drinking child alcoholics. Harry Potter (usually referred to as H.P. by our gravelly narrator or "Harry fucking Potter" when the character speaks in the third person) is a self-aggrandizing, power-hungry bloke who makes elaborate speeches, usually about himself. Ron becomes Ronnie the Bear, a deceptively simple child who houses a brain stuffed with chess knowledge that could defeat gods.
Hermione is the Wretched Harmony; here Neely makes some of his more childish jokes by usually insulting her looks. I must say I wasn't a fan of him picking on a then-child, but I suppose it's better than the creepy salivating over the older Emma Watson. She is depicted as an ugly girl riddled with self-pity; the cruel mocking gives way to one of the track's funniest moments when Ronnie says that he hopes Harmony "gets a new pillow to cry into" for Christmas.
The commentary takes bit to get going; the first act of the film is devoted entirely to Neely coming up with fresh ways to call the Dursleys fat. However, once classes begin at Hogwarts, Neely comes alive, occasionally stumbling or laughing at the line that popped into his head before saying it but always managing to come up with narration that sounds like narrative bubbles on a pulp fiction comic. He hilariously calls Flitwick "Professor Ugnaught" after the creatures in Cloud City in The Empire Strikes Back. He turns Quidditch into a display of homoeroticism and bad teeth. Neville's unfortunate broom ride becomes merely an annoying diversion from Harry's twisted thoughts.
The more the film drags on, the better Neely gets. I can't tell if how much of this he planned in his head (it's obvious he watched the film a few times to get a feel for it), but I'd venture to say not much other than names and places, because he gets more confident as the film progresses and his lines get wilder and wilder. By the time Harry and his gang enter the Forbidden Forest, nearly every line is golden.
As good as the improv is, I do wish Neely would have paused every now and then and rerecorded a bit in which he either broke character or fumbled a line. However, that would have likely broken his stream of consciousness, so it's hard to complain. Really, the only bad parts of this are Neely's loose footing in the first 30 minutes and the simple fact that he didn't do this for all the films (fingers crossed that that might change one day). He took a crap film and made it thoroughly entertaining. The best part? It's all on YouTube right now.