Simplify, simplify! Exaggerate, exaggerate!  Combine those strategies with skill and imagination and you can get immediate, public-pleasing results in comedy and satire. That's what happens in the case of "Pleasantville," the aptly and ironically named first feature by Gary Ross, the co-writer of the fantasy "Big," and the writer of the fanciful, political "Dave."

It is crystal-clear that Pleasantville is going to become a popular mega-hit and that just about all regular filmgoers know what to expect. Even so:

Siblings David and Jennifer are high-school seniors in 1998 and in an unnamed town They share the problem of an unhappily divorced mother and the problem of people their age. At a school assembly, the students are given a pessimistic report on the future: unemployment, AIDS, environmental disasters, etc. (This is not a gratuitous announcement, since its aim is to incite good grades that can make the difference in an increasingly competitive society).

Dave and Jennifer may be twins but have different personalities. The girl is what, way back when, used to be called "boy-crazy." Her brother takes refuge from the (presumed) unpleasantnesses of life by watching cable reruns of old, 1950s family-type sitcoms. An expert in the series "Pleasantville," he is about to enter and undoubtedly win  the $1.000 first prize in a contest  about "Pleasantville."

The two kids, following a nicely planned succession of events, and via a mysteriously appearing TV repairman, find themselves transported to and inside the "Pleasantville" sitcom, as the characters Dave and Mary Sue, the children of the impossibly neat and idealized (by 1950's standards pushed beyond their outer limits) household of Betty and George.

We are now in a Twilight Zone territory, but without that program's darkness -- at least not overtly. Getting from reality to fantasy also reminds me of the way Orpheus (in Jean Cocteau's eponymous film) goes to another world by entering a mirror.

"Pleasantville" reflects mores and manners of many a 50's sitcom, only taken to the limit. The opening, establishing scenes of the movie proper are in color. Set in April 1958, the program's world is, unsurprisingly, shown in black and white and shades of gray. What is surprising is that its world is strictly limited to the falsely "ideal," town of Pleasantville. There is nothing beyond its Main Street, which, reaching its end, loops back to its beginning. It is like those images of a coiled snake  biting its own tail.

There is no history. There are no books, or rather, there are book covers of some major works but the pages inside are blank. The high school has a winning basketball team where everyone scores baskets. One may wonder which other teams they play. Or where anything --no, make this everything else, from clothes to cars to meat --you-name it, comes from. But then "Pleasantville" requires blind, and willing, suspension of disbelief!

The sitcom is sanitized to the nth power. This goes beyond pristine picked fences, manicured lawns and perfectly surfaced streets, streets that you could fry the proverbial eggs on, except that the year-round temperature is 72 high, 72 low and never a cloud in sight. (How do they know what clouds are? Never mind). Not only are there no bathrooms mentioned, but Mary Sue's attempt to find one results in an room tiled and empty.

At a good clip, Mary Sue and Bud affect the place from A to Z. Since they "belong" in the sitcom, no one sees them, as we do, like those wiser extra-terrestrials of sci-fi flicks. So what they say and do is not questioned. Mary Sue gradually makes the sexual education of the youths, and, indeed, her own mother, in a neat reversal of the child teaching her mom the facts of life. Bud opens new doors, to art, to books (that have a content now), to feelings.

Among other transformations there is that of Mr. Johnson (Jeff Daniels), who seems to be a dimwit soda jerk until Bud, aware that Johnson has the repressed soul of an artist, releases it by opening his eyes with the gift of a coffee-table art book. If you use logic, you'll wonder where the book came from; and how its reproductions of paintings, from old to very modern, can affect so strongly a total visual illiterate. But the name of the game with this film is never to ask questions!

In another reversal, the local firemen do not put out fires, since these do not exist. Nor do they set fires, as they did in Ray Bradbury's (and Francois Tuffaut's) cautionary "Fahrenheit 451." They only know how to rescue cats from high branches.

Gradually, as the people of Pleasantville begin to change, feel and see new things, humans, objects, and nature go from black-and-white to beautiful colors. The colorizing does not, as a rule, affect the entire image but is applied to one item within it while the main view of the screen remains in black and white. Color shows up in often unexpected, symbolic places. The process is beautifully thought out and timed, superbly executed with digital techniques taken farther than in any film I can remember. Along with the invasions of color, natural phenomena such as rain also appear.

The first half of the movie is a delight, especially if you bear in mind that what it spoofs to the max is not really the life of the 1950s but life in certain 1950's TV programs. There is, however, a limit to one- or two-joke stories. The film's second part becomes increasingly like a view of 1950's society seen by militant eyes of the 1960s. The development  revs up its parables, takes us into matters concerning reactionary socio-politics, the mistrust of "the other" and of non-conformism, racism, suppression of ideas (down to a Nazi-ish book burning), fear of differences, and so on.

Things become a bit laborious. The underlying idea that change is good and inevitable, is a good one. Potshots at the 50s icons are supplemented by sometimes overt, sometimes subtler ironies about the 1990's. They imply that today trends, fads and above all conformism are, under various guises, not unlike those of 40 years ago. It is a sound notion to suggest that in the 90s we can be as self-centered or obscurantist as the Pleasantvillers. But the movie might have condensed all this and made its points in under 116 minutes.

Still, I cannot give too much weight to this objection since this elaboration, dotting of the i's and crossing of the t's, is better than the ponderously encapsulated didacticism that opens and closes the Twilight Zone's episodes. Pleasantville-the-movie has well-meaning allegorical ambitions, as well as a very tricky and a highly imaginative structure surrounding its exaggerations and simplifications.

It also has, with no exceptions, a splendid cast that can be touching (especially the characters played by Joan Allen and Jeff Daniels), serio-comic (the siblings), oddly pathetic (William H. Macy, and the smartly conceived heavy, J.T. Walsh in his last role).

Above all, it is infinitely more original and inventive than the pedestrian, copycat movies that make up the great majority of what goes on screens small and large, in this our time.