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The Big Bang Theory - Season 9 - Judd Hirsch Cast as Leonard's Father

Taxi alum Judd Hirsch has been tapped to guest star on the network's nerdy comedy, producers announced Wednesday at PaleyFest. Hirsch will make his debut in the May 12 season nine finale.

The casting marks the first time that Leonard's father will be seen on the veteran comedy. Details about the character have yet to be fully flushed out as producers are still working on the script for the finale. Showrunner Steve Molaro told THR on the red carpet that the episode might feature a cliffhanger.

"We're all honored to be invited to this James Burrows tribute … and we all had the opportunity to meet these incredible casts Jimmy directed and I had the opportunity to meet Judd Hirsch," Galecki said. "I ran up to him and bombarded him with conversation that went on for a long time about what a fan I am. I did share with him that when we were shooting the pilot, I rewatched the first two or three seasons of Taxi — not because I wanted to base Leonard on his character but the purpose his character served — this anchor in this group of people — and he was just as much at times a voice of reason as he was just as confused as everyone else. I shared that with him and a lightning bolt struck … or another merlot ... and I said, would you have any interest in playing my dad on the show?"