Izzy Mandelbaum is an 80-year-old man and resident of Del Boca Vista who can't stand to lose.
He has a son named Izzy Mandelbaum, Jr. and father Izzy Mandelbaum, Sr. who were both extremely old; they all work at a family restaurant known as the Magic Pan. Izzy is obsessed with physical fitness.
In "The English Patient," Izzy challenged Jerry Seinfeld to a weightlifting competition, which lands him in a hospital. His son and father do the same against Jerry. With all three of them in the hospital, Izzy hired Cosmo Kramer's Dominican friends to roll crepes at the Magic Pan, but they were rolled too tightly and hurt people.
In "The Blood," Izzy was later hired by Jerry's parents to be his physical trainer. Jerry's final workout with Izzy had Izzy and Izzy Mandelbaum Jr. driving Jerry's car with one end of the rope tied to Jerry as he jogs. When Izzy Jr. discovered blood splattering out of the brake part of the car and told his dad, Jerry fainted and got dragged enough to end up in the hospital. This resulted in a blood transfusion for Jerry from Newman much to the horror of Jerry, Kramer, and Newman.
- It's go time.
- Mandelbaum! Mandelbaum! Mandelbaum! (He and his father and son chant their last name)
- All aboard the pain train.
- If you want to live in a butcher shop, I'm gonna treat you like a piece of meat.
- What in holy hell?
- Step aside, string bean.
- You think you're better than me?
- Wrong attitude, you're not bringing that trash into my house.
- I see how it works now, he knocks me out of commission, so you can strut around in your fancy #1 shirt.