Cosmo Kramer, usually referred to by his surname, is a fictional character on the American television sitcom "Seinfeld" (1989–1998), played by Michael Richards.

The character is loosely based on comedian Kenny Kramer, Larry David's ex-neighbor across the hall. Kramer is the friend and neighbor of main character Jerry, who resides in Apartment 5B, and is friends with George and Elaine. Of the series' four central characters, only Kramer has no visible means of support; what few jobs he holds seem to be nothing more than larks, although he never seems to be short of money.

In "The Seinfeld Chronicles", the pilot episode of "Seinfeld", Kramer was originally called "Kessler" to prevent legal issues since it was based on Larry David's real-life next-door neighbor Kenny Kramer.

Like the other three characters, Kramer has pseudonyms he uses in various schemes.

Under the name H.E. Pennypacker in "The Puerto Rican Day", Kramer poses as a prospective buyer interested in an elegant apartment in order to use its bathroom. Kramer also appears as Pennypacker to help Elaine get revenge on a Mayan clothing store, "Putumayo", by repricing all the merchandise in the store with a pricing gun in "The Millennium".

As Dr. Martin van Nostrand, Kramer tries to get hold of Elaine's medical chart to erase the negative comments her doctor has made in "The Package".

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