Your humble reviewer is a tremendous fan of "Twilight Zone" episodes in which the protagonists are utterly insane, megalomaniacal, and hyperactive... And preferably all three at the same time! The best examples I can give are Oliver Crangle in "Four O'Clock" and Somerset Frisby in "Hocus Pocus and Frisby", both featuring in the third season. McNulty, the (anti-)hero in "A Kind of Stopwatch", would form the perfect trio with these other two loonies.
McNulty the type of guy who never - literally never - stops talking about his own opinions and ideas to improve the world, while constantly using irritating stop-phrases like "isn't that something?" or "you think about that now!". His mania costs him his job and all his friends at the local bar. What do you expect when you make suggestions such as making hotdogs flatter, so they look more like hamburgers, when you actually work for a company that sells women's underwear? I love this man! McNulty's life changes when he comes in possession of a stopwatch that literally freezes the world around him.
The plot itself is of lesser importance, especially because McNulty doesn't do anything useful with his magical device and ruins it as soon as he figures out the true power of it, but the episode is more than enjoyable if only for Richard Erdman as the hopeless McNulty. I sure hope he improvised most of his lines, otherwise it would have been a tough job memorizing everything.