People who criticize this movie are ones that don't have a humor bone whats so ever. They look at how incredibly corny this movie is, instead of looking at the goal of the movie, make you peppy after watching it. We tend to forget that the point of this movie was about having fun. The music was catchy and fun also. Another thing, you notice how everybody is well fit... they didn't have surgery options or 24 fitness centers back then people; its called take care of you body (minus slight drug usage :P)
Looking back at 60's movies, you can totally tell that they had massive stereotypes back then that if they tried doing in movies now-a-days, it would be massively protested: Biker Boys being incompetent, Boys using sexist statements, girls being overly sassy, and yes even the boy girl, boy girl parrying off everywhere haha. We can use the excuse that this is a classic and get away with it now, it just sucks in order to make a movie like this now would be shun in today's society.
Give it time and Hollywood will end up remaking this with Zac Efron or somebody which will suck. The characters will be little whining emo that had to much plastic surgery or they whole goal is working out.
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http://www.imdb.com/video/wab/vi604898585/