Explain This to Me?

 mattie kahn@mattiekahn

You don’t know this, but when I see your dog I make a mental note of whether or not they are Jewish

10:12 PM · Feb 14, 2022·Twitter for iPhone

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Is this an anti-Semitic Jew-dog joke?  A play on circumcision, I thought at first...? (No, dogs are castrated, not just have their foreskins removed...)

A cultural reference from a popular tv show I don't watch?  Help me out.