|Family||Wife: Doris Klompus|
|First Appearance||"The Pen"|
|Last Appearance||"The Money"|
|Portrayed By||Sandy Baron|
Jack was a short tempered resident of the The Pines of Mar Gables Phase II condos in Florida and seemed to consistently have a grudge against Morty Seinfeld (Jerry Seinfeld's dad) and was the condo association vice-president under him. He was famous for shouting "Ahh!" while waving his hand down, which is often how he would end an argument with Morty.
He carried a Space Pen, the kind used by astronauts, which could write upside-down. He showed it around and gave it to Jerry after the comedian complimented it, leading to consternation over whether it was a gift that should have been accepted.
In “The Raincoats,” Morty asked Jack to retrieve a box of leftover "Executive" raincoats from his garage and send them to him in New York. Because the garage was locked, Jack broke a window to get in, cutting his hand in the process. He neglected to fix the window, which allowed burglars to enter the Seinfelds’ home and rob them.
When Jerry bought his parents a Cadillac with the money he received for a show in Atlantic City as seen in "The Cadillac, Part 2," Jack was suspicious of Morty, thinking he stole the money from Del Boca Vista’s board of directors. Morty was president of the board and Jack among others voted to impeach him. The impeachment succeeded. Upon Mabel Choate remembering that Jerry was the one who mugged her for her marble rye upon Jack calling her an "old bag," she changed her vote from against impeachment to in favor of impeachment. As a result, Herb dismisses Morty and swears in Jack as the new condo president.
In "The Money," the Seinfelds ended up selling the Cadillac to Jack for $6,000 and tried to give the money to Jerry, who bought it back from Jack for $14,000. Jack proceeded to crash the car in Alligator Alley.