You can hear someone in the audience yelling "Oh no!" when George is told Mr. Pensky is there to see him.
When Jerry leads Gino out to the fire escape, you can see Jerry's bike in the background not moving. In the next shot, it's swaying back and forth.
If I'm not mistaken, it was Jerry himself who took revenge on Newman, not his barber.
Response: Correct, Jerry is the one who shaves off all of Newman's hair. This is shown when Jerry runs into Newman at the barber shop and grabs the electric shaver.
Jerry: So what do you do there all day?
George: They gave me the Pensky file.
Elaine: (auctioning off Kramer) He likes fruit, and uh, he just got a haircut.
George: I have an idea.
George: I show up.
Jerry: Whadya mean, you show up?
George: I show up! I pretend I have the job. The guy's on vacation. If I have the job, it's fine. If I don't have the job, by the time he comes back I'm ensconced.
Jerry: Hmmmmm… Not bad.
Enzo: (to Jerry) You tell-a the joke, I cut-a the hair.
Kramer: (talking to Newman on Jerry's phone) So, when are you gonna be able to go out?
Newman: (with a shaved head) Not for a while.
Newman: Can I use your bathroom?
Jerry: What's wrong with yours?
Newman: My toilet's clogged.
Jerry: You can't unclog it?
Jerry: Did you ask Kramer?
Newman: He's out.
Jerry: Number one?
Newman: Yes, yes. Can I go? Cause I gotta go very badly.
Jerry: All right. Flush twice.
Jerry: In the one minute he worked on me, I could tell he was really good.
George: What's the worst thing that could happen?
Jerry: Well, you'd be embarrassed and humiliated in front of a large group of people and have to walk out in shame with your tail between your legs.
George: Yeah, so?
Jerry: I want you to have this job. Of course, sodomy is a pre-requisite.
George: Ta ta, Tut-tel.
George: In college they used to call me 'The Little Bulldog'.
Newman: I almost went to barber school. I always felt I had a talent for it.
George: Yes, I like to feel cozy. You know, I have a very small apartment. I like to feel tucked in, nestled in. Love to be nestled.
Kramer: I could raise enough money to cure polio.
George: I enjoy understanding.
George: Well, a lot of people consider me small and prestigious.
Secretary: (through intercom): Mr. Costanza, Mr. Pensky is here to see you.
George: (nervously) Mr. Pensky? Of the Pensky file?
Kramer: I'd like to have shoehorn hands.
The music in the background for many of the scenes in this episode is from Rossini's opera "The Barber of Seville".
Many times in this episode people discuss the Tim Burton film "Edward Scissorhands."