A mother fucker, yeah I do it like your dad, bitch
“Motherfucker” is a term used to described an enemy or a bad person, but it literally means someone who fucks moms. So Webby claims that he is indeed a motherfucker, because he has sex with your mom.
Since this line comes right after the Dexter reference, this could be a reference to James Doakes' favorite word.
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