What’s your favorite episode?

Having just rewatched every episode again, beginning to end, my favorites from each season
S1 - The Stock Tip
S2 - The Jacket
S3 - The Boyfriend
S4 - The Junior Mint
S5 - The Marine Biologist
S6 - The Race
S7 - The Gum
S8 - The Chicken Roaster
S9 - The Merv Griffin Show

I can't think of another comedy series that featured so many great episodes.

If I had to pick just one, it would be The Marine Biologist.

My favorite is 'The Junk Mail.' All of the arcs are hilarious:

Kramer boycotting the mail ("Move along, Betty.") and then getting kidnapped by the postal service. ("You said a mailman I know, and you're a mailman I know!")

Jerry getting a van from his boyhood friend, Frank Merman, who turns out to be one of the 'dirt people'.

George is being ignored by his parents so he decides to date his cousin. ("You must be George's cousin." "Girlfriend." "All right.")

Elaine falls for The Wiz. ("What if we're out somewhere and you see the Maytag repairman?")

The scene where George discovers his parents having sex in the van. ("Oh, my god!")

Then the final scene with George and his parents:

"What you saw in that van was a natural expression of a man's love for his lady."
"Oh... make it stop."

Probably the episode from Season 2 where the guy who Jerry hired to clean his home steals George's statue and Kramer goes to the guy's apartment dressed as a cop to retrieve the statue.

There are so many, but had to search the episode names :) I only know them by content:) and can't rank them as well as they were all brilliant

The contest
The outing
The Tape
The soup Nazi
The mango
The wait out
The label maker
The fix up
The Merv griffin set
The chicken roaster
The smelly car
The nose job
The implant

A very underrated episode is The Diplomat's Club (S6,E21), as something bad happens to almost everyone, Jerry usually is excluded but he gets something bad happening to him as well. Elaine gets fired for supposedly trying to kill her boss, Mr. Pitt. George is accused of being racist and starts going through the city to find a black friend so he does not look racist to his boss and Jerry gets kicked out of his plane. Kramer lost a bundle of money betting on the flight Jerry got in.

I'm only about to start Season 4, but so far The Limo. Absolutely hilarious. The ending with "Donald O'Brien" had me laughing out loud.