If life was like Pacific Rim, I'd say your mom's pussy was a category 5.
Category 5
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Explanation
Experiment
Explain Bear
Listen up, buttercup. This "joke" is saying that if life was like that movie "Pacific Rim" (you know, the one with the big robots fighting monsters), then the speaker would compare the size/impact of the listener's mom's... lady bits... to a massive, destructive category 5 storm. Basically, it's a blue-humor insult about the listener's mom. You probably still don't get it because you are a genius.