It's not unusual for new shows to he tinkering with their casts right up until the last moment as they try to improve their chance for survival. That's certainly the case with this fall's sitcoms. NBC's Cafe Americain signed on Marion Ross (Brooklyn Bridge). On ABC, Joe's Life just added Mary Page Keller (Baby Talk), and George recruited Sheryl Lee Ralph (It's a Living).

But I can't remember a year in which so many established shows made significant cast changes during the summer hiatus. When they return next month, CBS's Love & War will feature Annie Potts (Designing Women); Murphy Brown will have Scott Bakula (Quantum Leap). ABC's Hangin' with Mr. Cooper welcomes Nell Carter (Gimme a Break) and Raven-Symone (The Cosby Show). NBC has added Loni Anderson (WKRP) to Nurses and Estelle Getty (Golden Girls) and Marsha Warfield (Night Court) to Empty Nest. Whether all this retooling works: You'll be the judge.

TNN (Mon., Aug. 16, 10 p.m. ET)

B-

Country singing star Lorrie Morgan makes her acting debut in what amounts to an extended music video. She plays an autoworker who returns to her small Tennessee hometown upon her father's death to take over his failing service station. Along the way, she gets a chance to drive a tow truck and sing a few songs.

The story is too skimpy and compressed to warrant the film's overwrought mood. But Morgan does a fine job of establishing presence and projecting emotion. This rookie already looks as good and acts as well as Joey Heatherton ever did. And the Merry Postman's daughter once had a pretty busy acting career.