Blame it on Regis. Maybe it was the allure of big prize money. Or the lack of anything better to watch. But we all fell for Who Wants To Be a Millionaire, the wildly successful game show that aired in prime time on ABC for 13 of 14 consecutive days last August.

On average, the trivia quiz show drew an audience of more than 14 million viewers a night - with the final episode, on August 29, attracting 22.4 million fans - making it the highest-rated show for the entire summer. Four of its seven broadcasts the first week finished in the top ten in household ratings, and it only picked up steam, claiming five of the top six spots the second week.

For Disney's ABC unit, which has struggled to stay competitive in prime time, Who Wants To Be a Millionaire was the mouse that roared.

The success of Millionaire, a copycat of the equally successful British show of the same name, has put more than a few industry wheels in motion, taking everyone, including ABC, by surprise.

Ironically, most of the commercials that aired during the show were make-goods for other programs, so some advertisers really got a bargain. The network knows better now, and is rushing to bring host Regis Philbin and company back this month for November sweeps, and may even turn it into a daily syndicated program. Meanwhile, some of the other nets are scrambling to come up with their own versions, and advertising executives are taking a closer look at the genre.

"It's a hit," says Fred Wostbrock, coauthor of The Encyclopedia of TV Game Shows (Checkmark Books) and a leading game show agent."It's like a motion picture that wins an Oscar in every category. That's magical."

Wostbrock and others say that ABC did everything right, including choosing the right host. As the popular co-host of the ABC morning show Live! With Regis and Kathie Lee, Philbin has tremendous name recognition and the power to promote Millionaire, Wostbrock says. His half-threatening, half-theatrical stance as he asks contestants "Is that your final answer?" only adds to the spectacle of the show - a spectacle made even more dramatic by flashing lights, thundering music, and a hokey, sci-fi set design.

"This was a game show done as an event, and that's different," says Janeen Bjork, a senior vice president and director of programming at Seltel, a New York City-based sales organization that advises TV stations on choosing shows.

In fact, ABC learned from the British version, now in its second season, creating urgency and demand by limiting Millionaire's run to two weeks. Lyle Schwartz, senior vice president and director of media research at The Media Edge, Young & Rubicam's media unit, likens the strategy to that of a short miniseries or the telenovellas popular with Spanish TV viewers. "You're told beforehand that this will last 13 days, and that's all you get," he says.

The most impressive coup for Millionaire, however, was its ability to draw large numbers of viewers among all age groups, performing strongly among kids, teens, young adults, and older viewers - a rare achievement in this age of audience fragmentation. On average, the game show drew an audience of 14.4 million across all demographics, skewing slightly higher with women 18 to 34.

A recent analysis by The Media Edge shows that Millionaire virtually mirrored the U.S. population in age distribution; in fact, the percentages of viewers ages 25 to 34, 35 to 44, 45 to 54, and 55 to 64 were almost identical to the U.S. percentages. By comparison, 60 percent of the viewers of The Wheel of Fortune, Jeopardy!, and The Price is Right are over 55, according to Nielsen Media Research.

Michael Davies, the show's British-born executive producer, says that broad demographics were what his network was shooting for."Our questions run the gamut in terms of knowledge and expertise, and that enables people of all ages to get involved. Families can sit down together and watch the show. We're very pleased about that." Davies was also co-creator of Win Ben Stein's Money on Comedy Central.

But Who Wants To Be a Millionaire is no ordinary game show, many are quick to point out. "When I saw clips from the British version, I thought to myself that this looked more exciting than any other game show I've seen in a long time," says Chris Geraci, senior vice president and group director for national TV buying at BBDO. Millionaire's quirky format allows a contestant who gets stuck on a question to use one of three "lifeline" options, such as calling a friend or asking the audience for help.

And an analysis of the U.S. show's minute-by-minute ratings points to a "rare" occurrence, according to Kate Lynch, vice president, U.S. research director at Leo Burnett's Starcom media unit: viewers leaving at regular intervals, probably during commercial breaks, and then returning in large numbers to continue watching. "It shows that this is not just some flash in the pan," she says.

Fans of the genre maintain that there is just something inherently attractive about game shows. More than 500 have aired nationally since they first gained popularity on American radio in the 1930s and '40s, including 27 that ran in the 1970s.

But will the success of Who Wants To Be a Millionaire spawn a resurgence of game shows on night-time TV? Even stalwarts like Jeopardy! and Wheel of Fortune - the top two syndicated shows in the history of television - don't draw the younger viewers who make for attractive prime-time fare. And market fragmentation has led to the development of cable outfits like The Game Show Network, the five-year-old Sony-owned cable channel, which is seen in over 22 million households.

Still, a hit's a hit. Although exact numbers weren't released, it is said that over a million Americans dialed the 900-number (at a cost of $1.50 per call) to apply to be a contestant on Millionaire. During the first three Millionaire series on British TV, more than 10 million people called in to enter.

The networks are taking the cue. CBS is already planning to revive the classic What's My Line? And ABC has a comedy game show in the works for next fall called Have I Got News For You, starring Norm MacDonald. Wostbrock also notes that there is talk about bringing back two '50s hits, The $64,000 Question and Twenty-One.

Millionaire has already made an impression with ad researchers and planners. Starcom's Lynch says her firm may soon undertake an analysis of the correlation between different genres of programming and viewers' attention levels. "Because a show like this is fast-paced and exciting, it gets people involved," she says. "It might be a very good vehicle for advertising."

The Media Edge's Schwartz says that game shows can be "a perfect environment for informational commercials," such as commercials in the form of a quiz.

Needless to say, all eyes will be on Millionaire's return this month, when it has to compete with strong and original sweeps competition from other networks.