In the wrestling business, they say that an up & coming wrestler will "get the rub" from working with veteran performers in a main event.
Filmation & NBC, realizing that The Kid Super Power Hour with Shazam! was dying, had to play a trump card, and have three of the kids from Hero High team with Captain Marvel to save Captain Marvel, Jr. & Mary Marvel from the evil Star Master. Unfortunately, while Glorious Gal, Weatherman, & Rex Ruthless "got the rub" from teaming with the Marvels, it didn't help them in the least bit. The series was cancelled after 1 season, and Hero High and its student body became a distant memory.
Here's "Star Master & the Solar Mirror", written by Tom Ruegger, who'd make his fame working at Hanna-Barbera & Warner Bros. later on.
I don't know whose idea it was to give Uncle Dudley (Uncle Marvel) a WC Fields-esque vocal pattern, but I'd have preferred the "Mentor" version from the live-action show.