Movies Pierce Brosnan may be best known for playing secret agents, but stepfathers are fast becoming a subspecialty. On the heels of his role as Sally Field's suitor in Mrs. Doubtfire, the former Remington Steele plays a dad-by-marriage in the mediocre thriller Don't Talk To Strangers (USA, Aug. 11, 9-11 p.m.). This time he gets hitchedto a St. Louis aerobics instructor (Shanna Reed), only to be terrorized by her alcoholic cop ex-husband (Terry O'Quinn, star of the superb 1987 shocker The Step-father). Unfortunately, the most frightening part of Strangers is how much O'Quinn, with his close-cropped fringe of hair and salt-and-pepper mustache, looks like Reed's ex-Major Dad spouse, Gerald McRaney. Sitcoms A pair of saucy blonds dominate HBO's sitcoms. On Dream On (HBO, Aug. 10, 10-10:30 p.m.), flaxen-haired fireplug Toby (Denny Dillon) nurses her boss, Martin (Brian Benben), after he wrenches his back trying out the positions in an erotic manual he's editing. Then Sharon Stone guests on The Larry Sanders Show (HBO, Aug. 10, 10:30-11 p.m.) and winds up dating Larry (Garry Shandling)-until he decides he can't go out with someone who's more famous than he is. Funny, Larry didn't have the same problem earlier this season when he wooed Mimi Rogers. Guess Sharon's a notch up from Mimi on the star-dating food chain.

Cartoons Just when The Real World's Puck has eclipsed Beavis and Butt-head as MTV's premier enfant terrible, along come The Brothers Grunt (MTV, Mondays- Thursdays, starting Aug. 15, 7-7:30 p.m.) to outgross them all. A sextet of grotesque, gluttonous, monosyllabic siblings named after crooners (Sammy, Frank, Tony, Perry, Dean, and Bing), the Grunts were raised in a monastery and have a profound love of cheese. And in the don't-try-this-at- home department, the Grunt boys have their own disgusting shtick to match Puck's snot rockets and B and B's frog baseball: nipple pinching. Ouch!

A much more socially redeeming 'toon, Whitewash (HBO, Aug. 16, 7:30-8 p.m.), animates the fact-based story of an African-American schoolgirl who had her face spray-painted white by a gang of racist toughs in the Bronx. Penned by playwright Ntozake Shange and directed by Michael Sporn (Ira Sleeps Over), the stark Whitewash paints an unflattering portrait of the tabloid frenzy surrounding the 1992 incident. Linda Lavin's voice grates as a didactic teacher, ''Ms. Steunberg,'' but the always-soothing Ruby Dee lends a welcome presence as the girl's grandmother. Whitewash manages to be both PC and thought-provoking, a rarity among kids' TV shows.

Documentaries Michael Moore's NBC news-mag, TV Nation, isn't the only place to find pointedly political nonfiction this summer. p.o.v.: The Times Of A Sign-A Folk History Of The Iran-Contra Scandal (PBS, Aug. 9, check local listings) chronicles the case of Bill Breeden, a long-haired, teepee-dwelling Hoosier who served four days in jail for swiping a street sign to protest the naming of a street after Iran-contra coconspirator Adm. John Poindexter in his hometown of Odon, Ind. David Goldsmith and Steve Day's 40-minute short drives home a serious message (''I think it's really stupid that Bill Breeden had to go to jail and Poindexter, North, and Reagan got away with it,'' a local youngster observes) with frequent flashes of absurd subversive humor. If TV Nation gets renewed, Moore should sign up Goldsmith and Day pronto.