The law of diminishing returns is in full effect in "Austin Powers in Goldmember," the third in what will no doubt be many more sequels to the spy spoof "Austin Powers, International Man of Mystery."

Writer-actor Mike Myers is aboard again -- this time playing no fewer than four characters, among them lascivious secret agent Powers, villainous Dr. Evil and the gold-loving eunuch of the title. Once again teaming with director Jay Roach and the gamely goofy cast that has carried three films now, Myers has taken Austin from being an earnestly spunky homage to English spy movies to a bankable film franchise, complete with crass product placement and an inexplicable berth in the popular consciousness ("Yeah, baby!").

After three movies, Myers, a notorious prefectionist or control freak, depending on your point of view, has distilled the Austin formula down to a core cast of characters, catch phrases, running gags and motifs. He's a comedian who knows what the audience wants and isn't afraid to give it to them in the most finely crafted way possible.

The end result is exactly what made the first film popular to begin with, but two movies later the novelty can no longer carry the movie -- sure, it's charming, but it's the same kind of charming, which is the problem.

In this installment, Austin finally catches Dr. Evil, and with the good doctor behind bars the time-displaced super-spy tackles a more personal problem: the apparent kidnapping of his absentee father, Nigel Powers (played by Michael Caine. Yes, Michael Caine.).

Austin tracks his dad back through time to 1975, where he makes contact with double agent Foxxy Cleopatra (singer Beyonce Knowles of Destiny's Child) and his father's abductor, Dutch hedonist Goldmember, who is in Dr. Evil's employ and hiding out in the past while working on a secret Doomsday Project. Father, son, and love interest pursue Goldmember back to the present, where he joins the escaped Dr. Evil and puts their plan into motion.

What counts in an Austin Powers movie isn't the plot, but the jokes. Packed with puns, improvisations, musical numbers, scatological jokes and admirably elaborate sight gags a la Benny Hill, "Goldmember" sticks to the first two films' method of throwing every conceivable joke out and seeing what sticks.

An opening salvo of inspired celebrity cameos degenerates quickly into a series of guest spots that date the movie more than Austin's wardrobe ever could; the "mole" joke featured prominently in the television commercials was done first and better in "Uncle Buck."

The humor in "Goldmember" falls uniformly along these lines: hilarious moments buried in repetitive, pandering jokes -- it's Myers's commitment to the material that even makes most of it convincing. There's plenty to laugh at, like the (somewhat overdone) subtitles gag and Dr. Evil's son, Scott (the always funny Seth Green), trying to join the family business. But the laughs are the same laughs -- no joke from the first two films has been left unturned.

The good news and the bad news is: it's the same old Austin Powers we all know and love. While you can't help but buy into the antic sensibilities of Mike Myers, there's still the nagging feeling that it was all a bit fresher the first, and even second, time around.

"Goldmember" is now showing everywhere.