In the final scene where Kramer is being blasted by his new shower head, he is never really in the stream of water. Michael Richards would have been game, I'm sure, but they probably did it that way to keep the camera from getting hit with reflected spray.
When Mrs. Seinfeld is trying to pick a glass for Elaine's urine sample, we get a close-up view of Jerry's cereal boxes. All identifiable labels are of Post cereals (Honey-Combs, Grape-Nuts, Post Bran Flakes, etc.). Clearly, Post Cereals paid for these product placements.
When Jerry picks up the phone to talk to his Dad, the antenna is down but in the next shot it's up.
By the end of the show, when Elaine and Jerry's mother are trying to choose a cup to place the urine, you can clearly see the reflection of a TV and what appears to be a cameraman on the cupboard glass.
There's a Comedy Central magnet on Jerry's refrigerator.
In "The Puffy Shirt" George tells Jerry that is mom, Estelle, has never laughed, ever. Then later in the episode the point is proven when Jerry tries to tell her a joke and she's not interested.
But in "The Shower Head" Estelle laughs at Jerry's joke: "Actually I'm drunk."
Maybe this is her first time laughing ever.
In this episode, Kramer offers some chicken to Elaine, and she eats it. In "The Stranded" she said that the only meat she will eat is fish.
After replacing Kramer's shower head to the low flaw kind, Kramer tries taking a bath as if it's his first time.
Kramer feels disappointed and disguisted by the concept of bathing.
On the other hand, on a former episode "The Wife" Kramer clearly states that he takes bath instead of showering.
Frank: (to Jerry's dad) This is Frank Costanza. You think you can keep us out of Florida? We're moving in lock, stock and barrel. We're gonna be in the pool. We're gonna be in the clubhouse. We're gonna be all over that shuffleboard court. And I dare you to keep me out!
Newman: Now here's the lowdown. Through a certain connection, I've been able to locate some black market shower heads. They're all made in the former Yugoslavia. And from what I hear, the Serbs are fanatic about their showers.
Jerry: Not from the footage I've seen.
Kramer: If I don't have a good shower, I am not myself. I feel weak and ineffectual. I'm not Kramer.
Jerry: (about his parents) You see this? Any thought pops into their head, they're calling me because it's a local call now. I'm used to a 1200-mile buffer zone. I can't handle this. Plus, I've got the dinners, I've got the pop-in's. They pop-in! It's brutal.
Uncle Leo: Move back with Lydia???
Jerry: Come on, you're lucky to have anybody!
Uncle Leo: Last week you told me I was in my prime, I should be swingin'!
Jerry: Swinging?!? What are you, out of your mind? Look at you, you're disgusting! You're bald, you're paunchy, all kinds of sounds are emanating from your body 24 hours a day! If there's a woman that can take your presence for more than ten consecutive seconds, you should hang on to her like Grim Death! Which is not far off, by the way.
Uncle Leo: But she's an anti-Semite!
Jerry: Can you blame her???!!?
Peterman: Oh, Elaine…the toll road of denial is a long and dangerous one. The price-- your soul.
Estelle Costanza: We're moving to Florida.
George: What?! You're moving to Florida? That's wonderful! I'm so happy!!! (pauses) For you!!!
Jerry: (on phone) Hey, listen to this -- Uncle Leo broke up with his girlfriend because of the bit I did; she thought it was funny, so he accused HER of being an anti-Semite, they had a huge fight, and now he's moving back into his apartment! You know what this means? My parents are gonna go back to Florida! … What? … What number is this? … Oh, I'm terribly sorry. (hangs up)
Kramer: Elaine I need the good stuff!
George: My parent's are moving to Florida!!! Do you know why?
George: To spite your parents!
Jerry: To spite my parents? Your parents are crazy!
George: They're out of their minds!
Kramer: I just took a bath, Jerry. A bath!
Jerry: No good?
Kramer: It's disgusting. I'm sitting there in a tepid pool of my own filth. All kinds of microscopic parasites and organisms having sex all around me.
Julia Louis-Dreyfus was again unable to control her laughter in a scene with Michael Richards. During the scene where Peterman throws Kramer out of Elaine's office and slams the door on his head, Julia kept her eyes locked on the file cabinet by the door to avoid distraction from Michael's antics.
The discussion between Estelle and Frank and Morty and Helen about the availability of condos at Del Boco Vista is purposely reminiscent of Jerry's conversation with the Maestro about the available homes in Tuscany.
On 19 Feb 96 as part of the Late Show With David Letterman: Video Special II, Jerry and Jason appear doing a scene about sandwiches. David Letterman interrupts their dialog and put his two cents in, then Paul Shaffer arrives and takes Dave back to their show. After they leave Jerry quips to Jason, "What the opposite of Must See TV?" He then points to where Dave and Paul were standing.
Jerry: (to Uncle Leo, after he complains that the cook must be an anti-Semite because his hamburger was overcooked) Anyway, the point I was making before Goebbels made your hamburger is a man like you could be dating women twenty years younger.
This is a reference to Joseph Goebbels, a German politician and Nazi propaganda leader during World War II. Goebbels was one of Adolph Hitler's closest associates and a well-known anti-Semite.
Kramer and Newman buying black market shower heads, all laid out on a cloth, is reminiscent of the movie Taxi Driver (1976) in which Travis Bickle (Robert De Niro) buys hand guns in the same fashion.