When Lt. Bookman (Philip Baker Hall) visits Jerry (Jerry Seinfeld), he picks up a book from the shelf before putting it back again. The next scene shows the book in a different position.
It's said that Mr Heyman (Biff Yeager) was fired for giving George (Jason Alexander) a wedgie, but while the first camera shot shows Heyman reaching for the waistband, the next shot shows only the students with Heyman is standing back.
An exterior of main NY Public Library is shown. At the time, in addition of administrative offices, the main library was a research library and stacks were closed. The mid-town branch public library was located across 5th Avenue and on the South side of 40th Street.
Near the end, the gym-teacher-turned bum says "Can't-stand-ya, can't-stand-ya!" clearly, but his lips are barely moving.
The librarian, Marion, says Mr. Bookman worked there for 25 years when Jerry, George & Kramer goes to the library at the beginning. But when Mr. Bookman is at Jerry's apartment, he said that 1971 was his first year on the job. This episode was aired in 1991, so that would make him 20 years on the job, not 25 as the librarian stated earlier.
In this episode Jerry (Jerry Seinfeld) claims not to drink coffee and therefore doesn't have any when Mr. Bookman (Philip Baker Hall) asks for some. In the pilot, Good News, Bad News (1989), Jerry was seen drinking coffee.