Things move quickly in television -- but never more so than when ratings are low. With enviable dexterity, the producers of ABC's "The Redd Foxx Show" have overhauled the program, readjusted its focus, and given it a more Foxxian glint. The remodeled edition gets a special airing at 8:30 tonight on Channel 7; a second fresh episode airs in the show's regular time slot, Saturday at 8.

According to the evidence presented in these two installments, "The Redd Foxx Show" has improved roughly 345 percent.

Foxx, it seemed, was playing a character insufficiently crusty and too lovable to suit his abrasive comic persona. So two characters -- a waitress and an adopted teen-age daughter -- have been jettisoned and new characters written in as more suitable foils for his tireless ire.

Foxx still plays Al Hughes, proprietor of Al's Coffee Shop and newsstand somewhere in a pastel inner city, but he now has more formidable nemeses, mainly his ex-wife, played with a waspish bite by Beverly Todd, and her best friend Darcie, played by Ursaline Bryant. Like some dread mythological two-headed beast, they travel in pairs, these two, and their chief pleasure in life appears to be in badgering poor Al about his chronically belated alimony checks.

This gives Foxx the opportunity to mete out the kind of irascible verbal punishment familiar to fans of his old series "Sanford and Son." On tonight's episode, when confronted with ex-wife Felicia, he asks, "Does Dracula know you're out of the castle?" He tells her, "Every time I start to miss your body, I forget your mouth is attached to it." He calls the relationship "kind of a love-hate thing; I love to hate her."

The comedy may be basic, but Foxx's minimalist delivery gives it a certain pungency, and there is the occasional philosophical aside along the pithy lines of, "Loneliness makes you a stupid idiot." An additional character, Foxx's grown but slightly addled son, a former pro football star, is played by an actor named Sinbad.

He is a welcome addition, but it's the two slinky-silky dragon ladies who are the liveliest comic idea, and they bring out the best of the worst in Foxx. Rick Kellard and Stuart Sheslow wrote tonight's episode; Kellard wrote tomorrow night's. Originally, a punch line for one of tonight's jokes was the name of actor Ray Milland. Mr. Milland died Tuesday in Hollywood. So the punch line has been changed -- to "Mrs. Marcos."