It's funny because it's intentionally shitty
Like all other StrawberryClock movies, they are intentionally crappy. But, it's the sense of stupidity and spoofing the elements of a traditional movie that make it humourous, a style which only StrawberryClock has mastered.
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If I were to review all of his movies, the reviews would be very similar (both in catergory ratings AND in the body of text). For those who have been at NG for a while, his "flash" provides some good laughs.