The Shaggy Dog (ABC Sunday at 8:30...

The Shaggy Dog (ABC Sunday at 8:30 p.m.--to be completed next Sunday) pioneered Disney fantasy back in 1959. Tommy Kirk stars as a teen-ager who mysteriously turns into a sheep dog in this warm and largely amusing family film in which Fred MacMurray plays Kirk’s dog-hating father.

Conspiracy of Love (CBS Sunday at 9 p.m.) stars Robert Young and Drew Barrymore (on the cover) as grandfather and granddaughter who become victims of the divorce between Barrymore’s parents.

Eight Is Enough: A Family Reunion (NBC Sunday at 9 p.m.) is a TV movie reprise of a popular series. Dick Van Patten and Mary Frann star.

What Steve Martin, director Carl Reiner and their writing partner, George Gipe, have done in Dead Men Don’t Wear Plaid (Channel 13 Monday at 8 p.m.), their hilarious spoof of hard-boiled detective mysteries, is to incorporate clips from ‘40s films so that bumbling private eye Martin seems to be playing scenes with 19 stars. A delicious treat, especially for film buffs.

That’s Entertainment!, the wonderful compilation of cherished moments, kicks off a week of splendid MGM musicals Monday on Channel 5 at 8 p.m.

In the TV new movie Strange Voices (NBC Monday at 9 p.m.) Valerie Harper plays a mother coping with a mentally disturbed daughter (Nancy McKeon).

One of the finest of all TV movies, The Execution of Private Slovik, returns on Channel 7 Tuesday at 9 p.m. following Game Three of the World Series. A distinguished collaboration of director Lamont Johnson and writers-producers Richard Levinson and William Link, it is a powerful testament with the aura of Greek tragedy that tells of a World War II soldier who became the only American executed for desertion since the Civil War. Martin Sheen stars.

The Grey Fox (Channel 11 Wednesday at 8 p.m.) is a beautiful, quietly memorable and eminently satisfying film starring Richard Farnsworth as a courtly, silver-haired stagecoach bandit who emerges from prison, in 1901, after serving a 33-year sentence.

Faye Dunaway is a terrific Joan Crawford, but Mommie Dearest (Channel 13 Wednesday at 8 p.m.) plays like a limp parody of a bad Crawford movie.

Sadie and Son (CBS Wednesday at 9 p.m.) is a new TV movie comedy starring Debbie Reynolds and Brian McNamara as a mother-and-son New York police team.

Pennies From Heaven (Channel 5 Thursday at 8 p.m.) is the musical as an art film, a work of fantasy so stylized and sophisticated as to be rightly described as experimental. In the film, Steve Martin lip-syncs his way through Depression-era standards as a breezy Chicago sheet-music salesman who falls on hard times--and in love with demure schoolteacher Bernadette Peters. Directed by Herbert Ross and written by Dennis Potter, Pennies From Heaven is the story of this couple’s struggle to find a little happiness and joy in a bleak world far removed from the bright promises held out by all those songs so beloved by Martin.

Sam Whiskey (Channel 13 Friday at 8 p.m.), a delightfully unhackneyed and mischievous comedy Western finds the widow Angie Dickinson urging Burt Reynolds to recover $250,000 in gold bars from a steamboat wreck and put it back in the Denver mint before it’s missed and her late husband’s only fall from grace discovered.

Although not among the best of the Agatha Christie films, Ordeal by Innocence (Channel 5 Saturday at 8 p.m.) is reliably diverting and gains much from its setting, the 800-year-old coastal town of Dartmouth, where paleontologist Donald Sutherland finds himself investigating a murder. Sarah Miles, Christopher Plummer and Faye Dunaway (in a “Mommie Dearest”-like cameo) co-star. Also notable: Dave Brubeck’s rich and varied jazz score.

Selected evening cable fare: A Room With a View (Z Sunday at 7, Wednesday at 9); Gung Ho (Movie Channel Sunday at 9); From Here to Eternity (Cinemax Monday at 6); Steaming (SelecTV Monday at 7, Z Thursday at 9); Soft Skin (Bravo Monday at 8:30); The General (A&E; Monday at 9); McCabe and Mrs. Miller (Z Monday at 9); Shampoo (WGN Monday at 9:30); Two English Girls (Bravo Tuesday at 8:30); Dersu Uzala (Z Tuesday at 9); Saint Jack (Lifetime Wednesday at 7); When Willie Comes Marching Home (Z Wednesday at 7); Heaven Help Us (Cinemax Wednesday at 9:30); Born Yesterday (Z Thursday at 7); All the Way Home (Cinemax Friday at 6); Valley Girl (WGN Friday at 9:30); Beauty and the Beast (Bravo Saturday at 9); Salvador (Z Saturday at 9).