you're telling me a lao ganned this ma?
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Hello, 彼得格里芬 here to explain the joke. While on the surface it seems like an absurd variant of the "shrimp fried rice" joke, this is actually deeper than that. Laoganma/老干妈 would translate as something like "old godmother's" but if we pick other meanings for the separate words we can end up with something funny. Lao/老 means "old"; ganma/干妈 means "godmother", if we rip 干妈 apart we get 干 and 妈, 妈 translates as "mother" but 干 has various different meanings and, if we use it as a verb, one of those is "to fuck". Thus "you're telling me a lao ganned this ma?" could be interpreted as "you're telling me an old (person) fucked this mother?" This was 彼得格里芬, hope to see you all next time! 再见!