I like little touches, such as anyone who sees Elaine's horrible dancing happens to mutter an appalled "Sweet fancy Moses!" And Uncle Leo is routinely referred to as Uncle Leo - e.g. when he's signed for Jerry's broken stereo and Newman realises he can't get Jerry on mail fraud, he frowns at the signature, looks up and mutters "Uncle Leo?" as though that's actually what Uncle Leo wrote as his signature! Then when Jerry pleas clemency with the bookstore manager over Leo's shoplifting, the manager says "Ah yes, Uncle Leo." 
When Jerry mentions 'Leo' Kramer asks "Leo? Who's Leo?" JERRY: Uncle Leo. KRAMER: Oh, Uncle Leo. I forgot his first name.
Another minor gag I love is when the photo-store woman's colleague says the photos have been confiscated and hands her a business card, she frowns at it and says "Newman?" and we see it in close-up with literally just the US Mail logo and 'Newman'!
I mean, those are kind of surreal flourishes but they're not too extreme.
It always amuses me that the imposing black woman who works in the charity store is called Rebecca de Mornay, same as the diminutive blonde actor, and obviously a few of the audience find it funny as well judging from the titters when she says her name in both the episodes she appears in. When George is trying to palm off his flagged book she says "How about I jump over this counter and punch you in the brain?" 
