Back in the 1970s the United States actually intended to go metric, and consequently, NBC Saturday mornings aired cartoon shorts designed to teach kids metric. These were done by the Schoolhouse Rock people, but aren’t considered part of the latter series, which aired on rival ABC. The cartoons featured superheroes called the Metric Marvels, all of whom apparently decided that having been granted powers like strength and flight, the best use of these powers was to teach children the Metric System in song. The heroes were Meter Man, Super Celsius, Wonder Gram, and Liter Leader (note the American spellings). My memories are vague beyond a few verses here and there (“I’m your Liter Leader, I’m here to show you how.”) Sadly the heroes’ mission proved a familiar, and the Americans steadfastly stuck to the Imperial system at a time when even the countries of the Commonwealth had moved away from the Imperial system. Perhaps the Metric Marvels should have used their powers on more traditional pursuits such as beating up villains instead.
YouTube has one clip spotlighting the series as a whole, but at this time the actual shorts are nowhere to be found online or in any official release. Maybe someday, when the US is ready to take another crack at the Metric system that everyone else uses, the Metric Marvels will don their costumes again and resume their fight against the Imperial measuring system!