Scott Menville, son of writer Chuck Menville, was cast as Spanky. Impressionist Julie McWhirter (ex-Casper & The Angels) voiced Alfalfa and Woim, the sidekick of neighborhood bully Butch (B. J. Ward), with Patty Mahoney (ex-Far Out Space Nuts) as Darla.
Like Pac-Man, the Rascals lasted just 1 season of new episodes, which is a shame, but that is the network's fault for not recognizing the appeal of the characters. The other problem was that H-B stablemate Smurfs aired opposite the block over on NBC. Ballgame over.
Here's the episode, "Rascals' Revenge". Spanky (Menville) is the announcer in the cold open, and Pac-Man (Marty Ingels) queues up a commercial break leading to some Richie Rich shorts and a Pac-Man cartoon. However, the video cuts off at the end of the bumper.
Something got lost in the translation of the shorts to Saturday morning TV, notwithstanding that two other studios (or maybe just one?) had the license before H-B, as we've documented.