Fans of the white-bread sitcom "Full House" and other deadly-dull manifestations of wholesome family values will get their money's worth here as the Olsen Twins deliver their patented brand of elfin cuteness. Those who regard these unlikely child stars as an alien species from the Planet Spoiled Brat will be thunderstruck by their offbeat timing, spider-monkey grimacing, and horrifying air of self-assuredness. After their petty squabbles start to wear on the nerves of their mother, Rhonda Thompson (Cynthia Geary), siblings Sarah (Ashley Olsen) and Julie (Mary-Kate Olsen) decide to take a journey over to their grandmother's house. Rhonda, meanwhile, is harboring a crush on a local delivery man, Eddie (J. Eddie Peck). Eddie grows less flirtatious, however, after finding out that Rhonda is the mother of twins. En route to Grandma's, Sarah and Julie meet thieves Shirl (Rhea Perlman) and Harv (Jerry Van Dyke), who've been knocking over the area's package delivery trucks. The thieving duo think up a more lucrative scheme after finding the twin stowaways in the back of a truck they hijacked from Eddie. While police detective Gremp (Stuart Margolin) suspects Rhonda and Eddie of the heists after they hock the contents of a delivery truck to raise the ransom for the twins, Shirl and Harv prepare to exchange Julie and Sarah for cash at a carnival near Grandma's house. Complicating matters is Eddie's desire to retrieve a lottery ticket which he left with Sarah and Julie. The kidnap drop-off turns into a rowdy scene, as a result of the twins' wild ride on a runaway buckboard. Gremp arrests Eddie and Rhonda, but good-hearted Harv and Shirl fess up. Making it to the televised lottery drawing in the nick of time, Eddie jumps for joy as his preliminary ticket wins the big prize. Cleared of charges and suddenly wealthy, Eddie accepts Rhonda, Julie, and Sarah as a ready-made family. More sentimental slop from the unstoppable Olsen twins, this yuletide cheer is better-paced than, but not as kookily agreeable as, their Halloween celebration, DOUBLE DOUBLE TOIL AND TROUBLE. Because there's a time-honored market for sitcom cuteness, one must put on a parent's hat to evaluate this picture fairly. The movie does provide an accessible moral lesson for its young viewers, it is mildly amusing in a slapsticky way, and grade-schoolers might very well see themselves mirrored in the antics of the Olsen twins. Thus, this family flick must be considered a success within its modest limitations. Be forewarned that, if you are not a kid or if you harbor a W.C. Fieldsian contempt for pint-sized troupers, you may break out in hives at the sight of the Olsens. Non-talent at their level must be fought with every weapon in a discerning critic or viewer's arsenal.