Why didn't whoopi have fun making this film???

You wouldn't know it from watching Sister Act. Whoopi semed to have a good chemistry with a lot of the nuns. Their enjoyment seems very obvious. I'm afraid I can't give you an answer.
Sorry.

I didn't know this at all, but searching with google, gave me this article:

No one expected "Sister Act" to be as successful as it was — even Whoopi Goldberg. There were fights on the set, problems with Disney executives, and it was generally thought that the film would be an unhappy, quickly forgotten mess — like so many earlier Goldberg flicks.

But surprise, surprise, audiences embraced the picture, which, in spite of backstage problems, proved to be funny, witty and charming. Naturally, there was plenty of back-pedaling, as everyone associated with "Sister Act" suddenly wanted to be identified with it again.

Even after its initial success with critics and audiences, however, no one could have predicted the film would become one of last year's biggest hits.

When that happened, a sequel was assured. But like so many follow-ups — especially those that come too quickly after the original — "Sister Act 2: Back In the Habit" is merely a rehash of the first film, with less wit and charm (and a different set of writers and director).

This one is more a musical than a comedy, and that aspect of the film works to its advantage, after a rather disastrous opening Las Vegas medley of Motown tunes, that is. Once the film settles into a series of fairly satisfying musical set-pieces, it gets better. But it still never transcends what it is — a second-rate rehash of "Sister Act."

This time Goldberg is approached by the San Francisco sisters to return to the convent, so she can teach music to some troubled teens in her old high school. Once again, she goes undercover as a nun, trying to fool the befuddled priest in charge (Barnard Hughes) and the mean-spirited school administrator (James Coburn).

Most of the film's meager plot has Goldberg interacting with the kids, primarily with one young girl (Lauryn Hill) who has a huge chip on her shoulder. The young players are all good, but their stories are strictly the stuff of Hollywood cliches.

And with those kids and the priests at the school, there are far too many characters to keep track of, which results in the people who made such an impression in the first film getting short shrift. Kathy Najimy, Mary Wickes, Wendy Mak-kena and Maggie Smith are all back but are given very little screen time, which is also true of the bevy of new characters, including those played by Hughes, Coburn and Michael Jeter.

Dominating it all, however, is Goldberg, who makes up for a lot. And some of the musical numbers, especially in the film's second half, are indeed quite rousing. Even if they are too little too late.

"Sister Act 2: Back In the Habit" is rated PG for some mild vulgarity and a single profanity.

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This is the first I've heard of this and I have to admit I'm surprised. Whoopi looks like she's having a ball making this movie.

I do remember that back in the early 90"s Disney was a notoriously bad studio to work for. Bean counters running everything and actors treated like props. That's what I remember, right or wrong.