The news was revealed March 16 at a PaleyFest session for the Emmy-winning series. Galecki explained that he approached the former Taxi star at the recent NBC tribute for director James Burrows.

“I ran up to him and just kind of bombarded him with verbalization,” said Galecki. “I did share with him, and this is true, that when we were shooting the pilot I watched the first two or three seasons [of Taxi]. Not because I wanted to base Leonard on his character, but the purpose that his character served in this group of people. [He was] just as much, at times, a voice of reason as he was just as confused as everyone else."

The date of Hirsch's first appearance has not been announced. Fellow Tony winner Christine Baranski plays Leonard's mother. The show stars Jim Parsons, who was last on Broadway in Act of God, as Sheldon Cooper.

Hirsch is a Tony winner for his performances in I'm Not Rappaport and Conversations with My Father.