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For Hollywood, it's the Summer of the Part Threes.

Leading off is "Spider-Man 3," which will surely weave its web around moviegoers' dollars this weekend. Hot on Spidey's heels is band of big-money buccaneers who will try to loot the box office with "Pirates of the Caribbean: At World's End" only three weeks later.

And these are only two of the likely blockbusters hitting theaters in a season packed claustrophobically tight with big franchise sequels — including four other "threepeat" films: "Shrek the Third" (May 18), "Ocean's Thirteen" (June 8), "The Bourne Ultimatum" (Aug. 3) and "Rush Hour 3" (Aug. 10) — the second installment of which had the highest opening comedy weekend box office gross (on a non-holiday) in history.

"It's a circus out there, a slate so full that Hollywood has never seen its like before," said Jeff Bock, analyst for box-office tracking firm Exhibitor Relations. "Most analysts predict this will be the biggest summer on record, and this enormous '07 slate could set a new standard."

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"Spider-Man 3," the first major release this summer, and "Shrek the Third" offer the biggest threats to toppling the third go-round of "Pirates" (May 25), whose second installment broke records last summer.

"Spider-Man" is the only part-three movie this summer whose second installment made less money then the first, but don't count out the web-slinging wallcrawler just yet.

"For 'Spider-Man,' being first out of the gate will really help. It's got two weeks before any major blockbuster comes out, plus loads of hype and star power, to pull in the bulk of its cash," said William Luhr, professor of English and film at Saint Peter's College in New Jersey.

The film already saw record-setting opening-day ticket revenues in Asia on Tuesday — raking in a $29.15 million worldwide first-day haul and topping the first-day grosses for Spideys 1 and 2 in both Japan and South Korea. It enjoyed the biggest opening-day ever for any film in Hong Kong and South Korea.

But hopes for "Shrek the Third" are high; three years ago, DreamWorks' goofy, lovesick green ogre landed the biggest single-day gross ever with "Shrek 2."

The makers of "Shrek the Third" also plan to capitalize on a market saturated by action films — hoping parents steering their kids away from violent summer flicks will land right in their fantasy world.

"Everyone knows 'Shrek' will be, pardon the pun, a monster. It's a double-whammy, a well-known product that's huge with kids. Parents will take their kids to this before anything," said Luhr.

Also cashing in on kid-power, the tousle-haired, bespectacled boy wizard's return in "Harry Potter and the Order of the Phoenix" (July 13) will seek to conjure moviegoers' money into Warner Bros.' coffers.

With the fifth "Potter" movie's release date craftily timed just one week before the wildly anticipated July 21 release of author J.K. Rowling's seventh and final book in her series about Hogwarts school for young wizards, "Harry Potter and the Deathly Hallows," the new film threatens to work some serious midsummer magic.

"With the new 'Potter' movie set for release just a week before the last book comes out, you have to expect that it's a potential juggernaut; the last novel was the fastest-selling book in history," Bock said. "The last film 'Goblet of Fire' really resurged a franchise that before saw each film making less and less money — the 'Order of the Phoenix' will definitely fly."

And to satisfy audiences' desire for technological terror, Universal's "Transformers" (July 4), directed by Michael Bay and produced by Steven Spielberg, hits theaters on what will be a key five-day Independence Day weekend for many Americans.

One of this summer's few non-sequels, "Transformers" draws its inspiration from the beloved children's toys of the 1980s and the Saturday morning cartoon show based upon them — which also spawned a kid-friendly cartoon movie version in 1986.

"Bay and Spielberg, that's a blockbuster team that knows how to wow an audience. Who knows, this film might be the one to overwhelm all of the part threes," said Christopher Sharrett, a professor of communications and film studies at Seton Hall University in New Jersey.

"It's original and plays into the pop culture of several generations — with the toys and an interesting live-action portrayal of the '80s animated show. This might be the movie that has the cachet of the summer."

In case you were born after 1990, Transformers are alien robots that battle each other and turn into cars, trucks, guns and, er, other stuff.

Another non-sequel summer release that harkens back to the '80s is 20th Century FOX's "The Simpsons Movie" (July 27).

Homer and his quirky, yellow cartoon family from Springfield, USA, aim straight for the belly-laugh audience in a movie fans of the wildly successful, nearly two-decade-old Sunday comedy saw as a long time coming.

"I'm sure the movie will be a hit," Sharrett said.

Yet another summer offering might seem to be original if it wasn't already made by John Waters in 1988. "Hairspray" (July 20), a remake this time based upon the Broadway musical, seeks to serve up the same "razzle dazzle" as "Chicago" or maybe "Dreamgirls" at the box office — this time employing the skills of, oh, John Travolta in drag.

"This could end up being kind of a mid-level hit like 'The Producers' re-make," Luhr said. "Travolta sure does look funny dressed up in his little outfit."

Another big-budget comic-book sequel will also try to ride Spider-Man's coattails this summer. "Fantastic Four: Rise of the Silver Surfer" (June 15) may be this summer's most confusing release. The first installment shocked all the critics by performing well at the box office despite being almost universally panned by reviewers and fans alike.

"I'll see it, but I don't think it's going to be very good," rabid "Fantastic Four" fan Matthew Hancock said. "I hope it is, but they might just be trying to feed off of the Spider-Man money."

And how could a sequel-packed summer be complete without John McClane (Bruce Willis) getting in on the action for a fourth time in "Live Free or Die Hard" — fighting, you guessed it, terrorists attacking the United States (through the Internet).

"The problem this new 'Die Hard' film will have is the same one the James Bond franchise started to have, which is that it had to compete with itself," Luhr said. "Both of these action series spawned so many imitators, the question is can it compete at the box office with all of them — and so many modern action films rip off the original 'Die Hard.'"

McClane faces the same dilemma as all of the other big-money behemoths in his path — can each of these pricey mega-movies stand out in the crowd with such a packed summer slate, or will audiences not be able to see the forest for the blockbusters?

"The sheer number of high-profile films is astounding, the studios just have to hope audiences will be able to absorb this many and not have sequelitis," Bock said.

Some critics say the "Summer of the Part Threes" puts the ball in the audience's court to say "no more" to so many sequels and push for a little originality out of Tinseltown.

"The 'Summer of the Threes' really gives one pause. All of these films could possibly sink — sending a strong message to Hollywood that these films trying to milk the franchise for all it's worth might really just be making people sick of franchises that have worn out their welcome," Sharrett said.

However, "Summer of the Threes" or not, fans seem to be psyched for what this season has to offer.

"This summer there's just so much coming out, you have to be excited," Hancock said. "With 'Transformers' you have the nostalgia factor, and with 'Spider-Man' the last movie was 10 times better than the first one, and there's three new villains and of course I'm a really big nerd too — so I'm really excited."