2002's "Scooby-Doo," the live-action adaptation of the popular Hanna-Barbera cartoon of the late '60s and early '70s, may have been financially successful enough for Warner Brothers to greenlight a sequel, but it had few actual fans. A slapdash effort that mostly strung together scenes without any care put into their narrative development, the film also fell victim to its one-sided aim for pint-sized viewers: simply put, it was far too childish for those fans that remembered the original Saturday morning show.

While hardly life-changing, "Scooby-Doo 2: Monsters Unleashed" corrects many of the problems that plagued its predecessor and returns to the general feel and campy creativity of the animated series. There are a handful of woefully unnecessary flatulence jokes, to be sure, but overlooking these brief and tedious interludes is to the benefit of returning director Raja Gosnell and screenwriter James Gunn (2004's "Dawn of the Dead"). In reuniting his bright, young cast, Gosnell has found better use for each of the Mystery Inc. gang, while executing a number of tighter, more entertaining chase sequences. And scripter Gunn has concocted an infinitely more original story, paying affectionate homage to his source material. Unlike in the lazy original, the machinations of the plot do not feel like a string of loosely related skits, but something more tautly planned out. Think of "Scooby-Doo 2: Monsters Unleashed" as a more kid-friendly, supernaturally-themed version of the "Charlie's Angels" motion pictures, and you will have a pretty accurate idea of what you are in for.

Since their last adventure, the gang of Mystery Inc.—pretty-boy leader Fred (Freddie Prinze Jr.), bubbly Daphne (Sarah Michelle Gellar), brainy Velma (Linda Cardellini), and goofy, hippie-like duo Shaggy (Matthew Lillard) and Scooby-Doo (voiced by Neil Fanning)—have become top celebrities in their hometown of Coolsville. After being seized at the opening of a museum exhibit by a masked villain and a Pterodactyl Ghost, they set out to solve their latest spooky mystery. Is the culprit Patrick (Seth Green), the art curator whom Velma has a crush on? Or is it the suspicious Old Man Wickles (Peter Boyle)? Or is it meddling news reporter Heather (Alicia Silverstone), whose every story on Mystery Inc. is edited to sound negative?

As Shaggy and Scooby try to prove their worth within the group, Coolsville is soon besieged by an increasing number of baddies, including The Creeper, Captain Cutler, and the 10,000 Volt Ghost. Will Fred, Daphne, Velma, Shaggy, and Scooby unmask the villain and save the day? Will there be a second sequel if this one is also a box-office hit?

"Scooby-Doo 2: Monsters Unleashed" is a more satisfying overall film than its precursor for a number of reasons. For one, its scope is grander and more ambitious, filled with a colorfully sumptuous production design by Bill Boes (2001's "Monkeybone"), inventively swirling cinematography by Oliver Wood (2003's "Freaky Friday"), and dazzlingly cheesy wall-to-wall visual effects. Take, for example, the elaborate sequence in which Shaggy and Scooby are chased down a steep slope and over a cliff by two skeletons. The way in which the camera freely zooms around its subjects, defying gravity in the process, is invigorating. Meanwhile, the conception of the plot and its many unraveling developments are carried out with a higher level of intrigue and showmanship. You really believe that each scene has a specific purpose in the bigger scheme of things, rather than there to merely pad out the running time, which the first one was all about.

Likewise, the four human leads are given fuller, more satisfying character arcs, as each one grows self-conscious of how much they contribute to the group as a whole, and must come to discover on their own that they are important. This is especially welcome of Fred and Daphne, who mostly stood along the sidelines in the original but this time get in on the action. Freddie Prinze Jr. (2001's "Summer Catch") and Sarah Michelle Gellar (1999's "Cruel Intentions"), married in real life, share a winning, lightly romantic chemistry. It is no secret that Gellar is a fine actress—her superlative work on TV's now-defunct "Buffy the Vampire Slayer" deserved Emmy consideration—but Prinze Jr. surprises in that he avoids eliciting pain on the viewer like most of his stiff performances do.

Meanwhile, the underrated Matthew Lillard (2004's "The Perfect Score") recaptures his uncanny Shaggy persona, screeching voice intact, while showing his usual comic flair. And Linda Cardellini (2001's "Legally Blonde") is just right as the mousy, intelligent Velma, who tries to impress Patrick at one point by dressing in skin-tight leather gear. In key supporting roles, Seth Green (2003's "The Italian Job") and Alicia Silverstone (1999's "Blast from the Past") may be fun celebrity faces to have pop up, but both performers deserve much better than goofy extended cameos.

Judging it solely on its merits as a worthwhile family film, one with the ability to divert the attentions of both kids and adults, "Scooby-Doo 2: Monsters Unleashed" is a rare superior sequel with nice character work threaded throughout the wacky hijinks and ghost invasions. And despite occasionally giving in to the temptations of excess—a flash-in-the-pan musical appearance by "American Idol" winner Ruben Studdard here, an overabundance of fart humor there—these missteps do not prove catastrophic to the otherwise likable, breezy tone. "Scooby-Doo 2: Monsters Unleashed" may be all but forgotten in a few weeks, but it has a warm heart and imagination to spare.