Blossom (7:30 p.m., Ch. 2) gets the "sneak preview" treatment nestled in behind high-rated Cosby (7 p.m., Ch. 2) before heading off for its regular time slot on Mondays at 7:30 p.m.

It's a sitcom about a 14-year-old girl, appealingly played by Mayim Bialik, who's best known for portraying the young Bette Midler in the movie "Beaches."Blossom lives with her musician dad, Ted Wass ("Soap"), and her two brothers - Anthony (Michael Stoyanov), a recovering alcoholic and drug addict, and Joey (Joey Lawrence of "Gimme a Break"), a dimwitted high school jock.

Tonight's episode is a stab at reality - sitcom style, of course. Blossom moves into puberty with the accompanying physical changes, and because her mother is absent she doesn't quite know who to turn to. "Cosby's" Phylicia Rashad shows up in a fantasy sequence.

It's pretty average stuff, as far as sitcoms go. Not bad, but certainly not terribly good, and reminiscent of dozens of other shows you've seen.

The best news is that it's replacing the awful "Ferris Bueller" on NBC's schedule. And almost anything would be an improvement over "Ferris."

ELSEWHERE ON THE TUBE: Dowling is framed for a bank robbery committed by his evil twin brother (I am not making this up) on The Father Dowling Mysteries (7 p.m., Ch. 4); Sada Thompson, who used to be the wonderful Kate on "Family," shows up as a mother of a different sort - Carla's - on Cheers (8 p.m., Ch. 2); Wings (8:30 p.m., Ch. 2), which has been dying on Friday nights, moves to Thursdays (and it's a whole lot better than the canceled "Grand") with a story about Helen taking flying lessons; Brenda is getting serious - too serious - with her boyfriend on Beverly Hills, 90210 (8 p.m., Ch. 13); Abby, who once killed an intruder with a gun, appears on "Phil Donahue" to discuss gun control on L.A. Law (9 p.m., Ch. 2) and Donahue appears as himself; PrimeTime Live (9 p.m., Ch. 4) profiles a terrorist; and Greg is back at work and Linda is spinning webs on Knots Landing (9 p.m., Ch. 5).-

LOOKING TOWARD FRIDAY: Sam leaps into the life of a teenager who must keep his family together on Quantum Leap (7 p.m., Ch. 2); "Paradise" returns with a new name - The Guns of Paradise (7 p.m., Ch. 5); there are two episodes of Night Court (Ch. 2) - a new one at 8 p.m. and a rerun at 8:30 p.m.; Dallas (8 p.m., Ch. 5) moves up an hour; Great Performances (8 p.m., Ch. 7) presents "Don Giovanni"; 20/20 (9 p.m., Ch. 4) looks into small-group health insurers; and Sons and Daughters (9 p.m., Ch. 5) premieres.