The "Scary Movie" horror spoofs must be some kind of mutant, alien movie franchise. There's just no other explanation for the fact that the sequels actually keep getting better. And unlike the hilarious but indefensibly scattershot second installment, "Scary Movie 3" even has a coherent combo-platter plot.

Serving up campy twists on The Ring's" killer-videotape plot and the alien invasion from Signs" -- with a little mock-"8 Mile" thrown in for flava -- the story catches up with wide-eyed dingbat heroine Anna Faris (who goofed on Neve Campbell's "Scream" character in the first two films) after she has become a blonde TV reporter (a la Naomi Watts in "The Ring") who discovers the creepy VHS cassette that curses anyone who watches it to die horribly in seven days. But when she tries to warn the world of its dangers, her producer puts his foot down: "No more paranoid on-air rants about the supernatural!"

Meanwhile Charlie Sheen -- returning to the kind of parody he showed such a deadpan knack for in 1991's "Hot Shots!" -- plays a farmer and former priest (shades of Mel Gibson in "Signs") whose cornfields have been flattened in a mysterious "crop circle" that from above reads "Attack Here!" with an arrow pointing to his house.

Sheen gets one of the movie's funniest lines in a "Signs"-send-up flashback to his wife's severed-at-the-waist death. "You mean this is the last time I can talk to the top half?" he asks the sheriff. "How about the bottom half? Can I squeeze in a few minutes with that?"

Since even the most sidesplitting dialogue is never done justice when quoted in movie reviews (without Sheen's deadpan delivery it's just not the same), I won't provide too many laugh spoilers here, except to say that the movie's opening riff on the first scene of "The Ring" had me laughing so hard I knew I was in good hands.

Dolled up in absurdly miniscule Catholic schoolgirl get-ups, Jenny McCarthy and Pamela Anderson lampoon their professional bimbo personas, scaring each other with the urban legend of the spooky video -- which Pam mistakes for another underground tape with which she's more, ahem, intimately familiar -- before one of them turns up dead while the other stares blankly at her friend's disfigured and severed head asking, "Um, are you OK?"

Mistaking the video for something more incriminating is a running gag in "Scary Movie 3" ("It was New Orleans, I'd never had vodka before and I was out of beads!"), but while the flick finds jokes in every nook and cranny, it doesn't run off in 20 directions at once as its predecessors did under the slapdash writing and direction of the originating Wayans brothers (writer/actors Shawn and Marlon, and director Keenan Ivory).

This sequel has been handed off to the likes of veteran lampoon director David Zucker ("Airplane!," the "Naked Gun" movies) and screenwriters like satire specialist Pat Proft ("Real Genius," the "Naked Gun" and "Hot Shots!" flicks) and pop-culture cult-flick comedy guru Kevin Smith ("Clerks," "Chasing Amy," "Dogma," etc.). While all these guys have black marks on their filmographies, they rise to the occasion here, retaining the series' urban sense of humor (gangbangers turn up to fight the aliens then kill each other off instead), but adding more zing and sting -- and considerably more adept moviemaking behind the camera.

While slow in spots and packed with cameos (Queen Latifah, Eddie Griffin and George Carlin all have "Matrix"-mocking one-scene roles) "Scary 3" never loses sight of its central plot: What is the connection between the crop circle aliens and the videotape? (It's hilarious -- that's what it is.) But more importantly, the hit-to-miss joke ratio is about 20 to one.

"Lord of the Rings," the Coors Beer "Twins" ads, "The Others," "The Texas Chainsaw Massacre," child molesting priests and Michael Jackson, Mother Teresa, "American Idol's" Simon Cowell (playing himself) -- they all get skewered here, and that list is just off the top of my head.

The unevenness of the "Scary Movie" franchise is a lesson in how hard it can be to get spoof comedy right, but in this case the third time is definitely the charm.