fiddlesworth
It's from Shrek III. Shrek has a terrible itch in his bum, and he cannot scratch himself, so he asks a guy with a stick in his hand to scratch him. Shrek asked the guy his name and he answered Fiddlesworth, to which Shrek answered: "Perfect!".
Well, I can't understand where the joke is here.

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Answer

Hi Carlinos,  the name "Fiddlesworth" is a play on the phrase, "a fiddle's worth". It means  that Shrek only needed just a small amount of scratching with the stick to relieve his itch.

Answer

Me neither.  Perhaps there is more to it that you left out