I just saw the pilot episode and I never heard Jerry refer to Kramer as Kessler. Am I missing it or was he really called Kramer the entire show?

I think he does in the 1st scene in 5A, when K reveals Met game results blowing Jerry's tape viewing.
Other than that he was called Kramer the whole time.
Just a little inconsistancy, because as we are discussing in The Betrayal, 11 years back when he 1st moves in, J calls him Kessler, & K corrects him to Kramer.

Word has it that when the pilot (001 Good News, Bad News) was readying to air, they still weren't sure what they were going to call K in the show and the TV guide listed him as Kessler.
Kind of like in the ep 63/64 The Pilot when Kramer says they can't use his name.

In 160 The Blood, Morty & Helen were in town for old Marvin Kessler's funeral. I think he was from Jerry's building.

This is all one for your insider's thread :)
It was a inside joke about which name to use, then they refer back to it later. Good stuff.

He must've said it because why would Jerry tie that in to the Betrayal?

I stand corrected re: the 1st TV Guide listing of K-man.
I just saw this on Mike's(TheNewsGuy) (http://membres.lycos.fr/tnguym/Seinfeld_2s.html) site, a pretty reliable source:

>>>In the TV Guide entry for this episode, his character is credited as Hoffman. I assume that this is the way it appeared in the script somewhere along the way. There were probably a number of name changes for this character, while Kenny Kramer was deciding whether or not his name could be used.<<<

-old thread/new thought-

I was thinking about 137 The Bizzarro Jerry one of the other threads...
Remember Kramer's bizzarro world counterpart;
KEVIN: "Yeah! Hey - hey guys! Elaine, sit down. These are a couple of my friends. Uh, this is Gene... and this guy, we... just call "Feldman!"

If they wanted to be really trick & insider, in 137 they should have named the bizzarro kramer Hoffman (see my last post). Only full seinGeeks would know and 'Hoffman' would have worked great.

You may have been the only one to get the Hoffman connection;)

I wondered why they gave the Kramer opposite a Newman sounding name (Feldman) and the Newman opposite a more Kramer-like name (Fargus).