what happened to both Jerry's and George's original dads on Seinfeld

Jerry’s original dad, Morty Seinfeld, was recast after the first season: Philip Bruns played him first, then Barney Martin took over. George’s dad, Frank Costanza, was also recast: John Randolph played him originally, and Jerry Stiller became the permanent Frank later on.

What changed

• Jerry’s dad: Philip Bruns appeared first, but the show later switched to Barney Martin.

• George’s dad: John Randolph played Frank in an early appearance, then Jerry Stiller replaced him.

Why it happened

The main reason was creative: the producers wanted performances that fit the characters’ later, more memorable versions better. In Frank’s case, the recast also happened before the character became a much bigger part of the show.

A small Seinfeld quirk

A lot of fans notice Jerry’s dad changed, but fewer realize George’s dad did too, which makes it one of the show’s funnier behind-the-scenes recast oddities.

TL;DR: both dads were simply recast, and the versions most people remember are Barney Martin as Morty and Jerry Stiller as Frank.