Krantz Films introduced itself to audiences in 1966 as the company packaging The Marvel Superheroes Show here in the US, and Rocket Robin Hood in Canada. Unfortunately, after Rocket and Spider-Man ceased production in 1969, the studio simply faded away.
Rocket Robin Hood, like Spider-Man, which would follow the next year, lasted three seasons, and picked up future animation legend Ralph Bakshi as a producer-director. In this case, Bakshi came aboard in the final season, as he took over Spider-Man in its 2nd season.
The basic story is a futuristic reboot of the Robin Hood legend, set at the dawn of the 31st century. Aside from the setting, the story is the same. Robin and his Merry Men are outlaws, fighting the tyranny of Prince John. Bernard Cowan, who narrated each of the Marvel shorts, does the same honors here.
To give you an idea of what you might've missed, since there were so few American stations that picked up the show in syndication, here's the open & close, plus some bumper vignettes.
A golden opportunity was missed in the late 70's-early 80's when WPIX in NYC brought back the Marvel show, under the title Marvel Men, sans the actual opening & closing. The station was home to Rocket Robin Hood during its run, and had they retained rights by, say, 1980, they could've coupled the two shows together.