I can legitimately say that Noises Off is one of my favorite movies of all time. If you have never seen it, be prepared for what you're about to experience. The first time I watched this with my extended family we were all crying with laughter.
It takes a few minutes to get going. The first act is funny in its own right. It has lots of well-written lines, the "play within the play" is enjoyable and it lays the necessary groundwork for what is to come: the second and third acts. And even with all that preparation, when that second act gets rolling and everything starts to go wrong, the laughs absolutely do not stop.
The physical comedy in this movie is sublime: tightly choreographed and timed to perfection. Every actor has a great part to play. My personal favorite has to be John Ritter's character. All of his "you know"s and "I don't know"s kill me. Michael Caine and Carol Burnett are also standouts. But every cast member gets laughs, and for good reason. There are so many quotable lines from this movie. I think my sister and I could literally quote 75% of this movie.
There are a couple of dings that I have to mention. The framing narrative, with its rushed "happy ending" on Broadway, wasn't in the original play and feels totally out of place. After you've watched it 20+ times you may want to fast forward to the second act. But even so, Noises Off is a hidden 90's classic. Highly recommended.