When critics say a film is "cartoony," it's often an insult. The term has become shorthand for poorly plotted movies populated by two-dimensional characters and pumped full of superficial action and bright colors.

On all counts, "Scooby-Doo 2: Monsters Unleashed," the campy sequel based on the popular Hanna-Barbera animated series, is guilty.

But calling it "cartoony" would be an insult to six-minute masterpieces by Chuck Jones (of Bugs Bunny and Grinch fame), superhero fare by Paul Dini ("Tiny Tunes," "Batman: The Animated Series") and Seth MacFarlane's naughty yet cerebral "Family Guy." All of the above provide more wit, character development and laughs in 30 minutes than "Scooby-Doo 2" achieves in triple the time.

Having reconciled and reunited since their first silver screen outing, Fred (Freddie Prinze Jr.), Daphne (Sara Michelle Gellar), Shaggy (Matthew Lillard) and Velma (Linda Cardellini) return as Coolsville's celebrity sleuths with a cowardly pooch.

Digging deep into the series' nostalgia pockets, screenwriter James Gunn resurrects some of the cartoon's most famous characters when the costumes of Mystery Inc.'s villains (Capt. Cutler's Ghost, Pterodactyl Ghost, etc.) mysteriously spring to demonic life during a museum exhibition.

Curator Patrick (Seth Green), TV reporter Heather (Alicia Silverstone) and even Old Man Wickles (Peter Boyle, in hilarious typecasting) all put in cameos as love interests, red herring suspects or both. But the addition of new characters doesn't keep "Scooby 2" from carrying an air of "been there, done that" - and it wasn't that interesting to begin with.

Director Raja Gosnell, who directed Scooby's first film foray, continues to showcase production designer Bill Boes' amazing, eye candy sets (like Mystery Inc.'s groovy headquarters) and color-coded costumes. Even when the camera doesn't move, Boes' vibrant color palette provides a lush unreality for Hanna-Barbera's characters to settle into.

But in "Scooby-Doo 2" the lights are on, but no one is home. It doesn't bode particularly well for a film when the production designer delivers its most memorable work.

As Velma, Cardellini stretches her nerdy hot-girl persona into a plastic jumpsuit to catch the eye of museum egghead Patrick, while Shaggy and Scooby embark on a campaign to become "real detectives" like the rest of the gang. Lillard continues to channel Shaggy with creepy abandon, but he's given fewer actual jokes and a lot more mugging to do.

In the first "Scooby-Doo" movie, Gosnell had fun toying with the mythology of the gang, hinting that Shaggy and Scooby were really potheads, that Velma might be a lesbian, and that love between Daphne and Fred might not be so rosy. Absent this playfulness, the sequel's all-surface, no-substance approach makes you yearn for the original cartoon.

To call this a movie a dog would also be an insult to canines, so let's just say "Scooby-Doo 2" is a Scooby-Don't.