Courtesy of an executive still giddy from the staggering success of one of the box office's most critically reviled current releases, here's an insider's guide on How To Tell When You've Got A Monster Hit On Your Hands: "THE Nov. 11 test screening of "Alvin and the Chipmunks" was halfway over when the power in Westlake Village cut out. The emergency lights inside the Mann Village 8 came on, but most of preview guests still wouldn't leave their seats. After some 20 minutes in the near dark, 20th Century Fox canceled the screening — the last one possible before "Alvin" was locked and no more editing changes would be possible. As soon as the theater emptied, though, the power was restored, and the Fox executives were nearly trampled when the majority of the audience rushed back in. 'That was when I sort of said, "I think this movie is going to catch,"' said Elizabeth Gabler, whose Fox 2000 division joined with 20th Century Fox Animation to supervise production." [LAT]