Hollywood’s biggest movie draw to close out the season is a sequel — on television.

Disney Channel averaged a whopping 17.2 million viewers for its premiere of “High School Musical 2” on Friday night, making it the most-watched basic-cable telecast on record. It’s also the largest aud for any television program on any net in about three months.

The average audience for the premiere Friday, according to preliminary Nielsen estimates, makes it well more than double the 7.7 million who tuned in for the premiere of the original telepic in January 2006.

Of course, the original pic became a phenomenon, with millions of kids and tweens watching it multiple times over the last 19 months, helping build anticipation for its sequel to a fever-pitch. Disney also picked a great date for the weekend launch of the second pic, timed to the when youngsters were prepping for the return to school as well as the start of the summer cool-down at the box office.

An understated Disney Channel Worldwide entertainment prexy Gary Marsh said Sunday he was having a “good weekend.”

“This was our Super Bowl,” Marsh said. “I think we have officially crossed the line from ‘High School Musical’ the movie to ‘High School Musical’ the mania.”

And as big as the numbers are, no one will ever really know how many viewers actually caught “HSM2,” as countless viewing parties across the country put large groups of kids (and their parents) in front of the same set.

“What’s powerful to me, there was this desire to be a part of a collective experience,” Marsh said.

Disney-ABC Television Group prexy Anne Sweeney also had reason to smile Saturday.

“It’s very rare in our industry to catch lightning in a bottle creatively, but to do so twice in a row is almost unheard of,” Sweeney said. “Kudos to Rich Ross and his amazing team for doing just that, and for making television history Friday night.

“Their efforts have delivered a new important franchise for The Walt Disney Company, and a cultural touchstone for millions of kids and tweens around the world.”

Although Disney Channel doesn’t air commercials, the “High School Musical” phenomenon has already poured $100 million into Disney’s operating income, and has created a ripple effect — impacting every division, from international channels and home entertainment to theme parks, licensing and merchandising.

More than 170 million viewers worldwide watched the original movie, which has also sold 7.8 million DVDs globally. The first soundtrack also clocked sales of 7 million across the world.

The success of “High School Musical” rounds out what has been a big summer for cable — and Marsh said broadcasters will have to sit up and notice after looking at these numbers.

“If there wasn’t a wakeup call being sounded before, this was the clarion bell,” he said. “The networks have buried their heads in the sand for a long time. But cable is gaining the attention of audiences everywhere.”

Disney Channel execs were given a hint a few weeks ago that the demand for “HSM2” was pent-up: The 21st run of the first “High School Musical” pulled in 5.8 million viewers in late July.

So how does the channel top this weekend’s boffo perf? Marsh said he can’t even ask the question.

“We’re just enjoying the moment,” he said. “We’ll see how it plays itself out over the next weeks and months. We’ll get first information on record sales later this week.”

Marsh said he’s received friendly emails from rivals at Cartoon Network and Nickelodeon, one of whom jokingly referred to the telecast as their “Black Friday.” The “High School Musical” franchise is just one part of Disney Channel’s rise as a tween powerhouse, thanks also to series such as “Hannah Montana,” “The Suite Life of Zack and Cody” and earlier than that, “That’s So Raven.”

“It’s an overnight success that’s taken five years to achieve,” Marsh said. “A few years back we went after the tween audience that we felt had been ignored. It was a vacuum we decided to fill, with live action shows that represented the hopes and dreams of kids.”

Next up for the franchise, “High School Musical 3” is in the works as a theatrical release. Even though it won’t bow on the Disney Channel, Marsh said they’re still heavily involved in the film’s development and strategy.

A closer look at the Nielsens for the preem of “HSM2”:

The movie easily outdrew the previous record for a cable movie, set by TNT’s “Crossfire Trail” in January 2001 (15.5 million). And it also bested the previous basic-cable record audience for any telecast, 16.0 million for ESPN’s “Monday Night Football” game between New Orleans and Atlanta last September.

The movie drew 10 million viewers more than any other telecast Friday night (6.9 million for ABC’s “20/20”).

It’s the largest aud for any Friday telecast since an episode of NBC’s “Law & Order: SVU” in 2002.

It’s the largest audience for any movie on any network in more than 2½ years (18.7 million for “The Magic of Ordinary Days” on CBS in January 2005).

And it’s the most-watched telecast of any kind since May, when a handful of broadcast series, led by “American Idol” (30.7 million) and “Grey’s Anatomy” (22.6 million), wrapped their seasons before bigger crowds.

Roughly half of the 17.2 million viewers for “HSM2” (8.7 million) came from the net’s target 6-14 demo, meaning that the pic also drew a sizable business among older teens as well as adults.

In kids 6-11, the 6.1 million viewers for “High School Musical 2” makes it the most-watched program on record in this age-range — above even Super Bowls. And in tweens 9-14, its 5.9 million lags only the 2004 Super Bowl.

Cabler was used “HSM2” to lead into a special 15-minute preview of upcoming original series “Phineas & Ferb,” which drew 10.8 million viewers. And that was followed by a firstrun episode of “Hannah Montana” (10:20-10:45 p.m.), which drew 10.7 million viewers — basic cable’s most-watched series telecast of all time.

Disney Channel also aired “High School Musical” on Saturday and Sunday nights, with Nielsen expected to release viewership numbers for those plays, as well as cume totals for the weekend, on Tuesday.