Cosmo Kramer, usually referred to as simply "Kramer", 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, residing 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.
Like the other three characters, Kramer has pseudonyms he uses in various schemes; H.E. Pennypacker, Dr. Martin van Nostrand, and Professor Peter van Nostrand are the most popular. 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", though due to a mishap with the pricing gun, Pennypacker was forced to instead remove the desiccants from clothes in the store in order to render them "noticeably musty in five years". In this latter capacity, he claims Pennypacker is "a wealthy American industrialist." 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". He also uses the Van Nostrand alias in the episode "The Slicer", posing as a "Juilliard-trained dermatologist" for a cancer screening at George's company, Kruger Industrial Smoothing. Mr. Kruger later recognizes him as Dr. Van Nostrand in "The Strike", but does not notice when Kramer says he has to work a double shift at H&H Bagels, something a successful dermatologist certainly wouldn't have to do. Kramer uses the name Martin van Nostrand (without the "doctor" prefix) while auditioning for the role of himself on the show Jerry in "The Pilot, Part 1". Kramer poses as Professor Peter van Nostrand in "The Nose Job" in order to retrieve a favorite jacket from another man's apartment; Kramer's jacket, to which he attributes at least some of his amorous success, is a minor plot point in other episodes until, in "The Cheever Letters", he trades it to a Cuban embassy official for several boxes of authentic Cuban cigars. Kramer is also referred to as "Assman" in reference to the license plate the state of New York accidentally gave him in "The Fusilli Jerry". He is also occasionally called "the K-Man" ("The Barber", "The Bizarro Jerry", "The Busboy", "The Note", "The Hamptons", "The Scofflaw" and "The Soup Nazi"). A derogatory designation for Kramer has been "hipster doofus", a moniker assigned to him by a woman in a wheelchair he once dated in the episode "The Handicap Spot", and occasionally directed at him by Elaine, as in "The Glasses". The nickname was first used in The Atlantic Monthly review of Seinfeld.

Q: What were some of his pseudonyms?
A: H.E. Pennypacker, Dr. Martin van Nostrand, and Professor Peter van Nostrand are the most popular.

Q: Which episode did he use this name in?
A: Puerto Rican Day

Q: What happened in this episode?
A: 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

Q: Does he end up getting the apartment?
A: unknown

Q: What other names does he use?
A: and Professor Peter
Which episode does he use this name in?
Kramer tries to get hold of Elaine's medical chart to erase the negative comments her doctor has made in "The Package "The Slicer", Pennypacker is "a wealthy American industrialist." "The Package". "The Package".
"The Package".