LOS ANGELES, March 18 (UPI) -- Judd Hirsch will guest star on a forthcoming episode of The Big Bang Theory.
Leonard's dad, an anthropologist, was previously mentioned on the CBS series but has not been seen thus far. Hirsch is best known for playing Alex Rieger on Taxi and will appear on The Big Bang Theory Season 9 finale.
"I ran up to him and just kind of bombarded him with verbalization," Galecki said of Hirsch. "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]."
"[Alex and Leonard are] just as much, at times, a voice of reason as [they are] just as confused as everyone else," he explained. "It just kind of went from there."
The Big Bang Theory co-stars Kaley Cuoco, Jim Parsons, Simon Helberg and Kunal Nayyar and airs Thursdays at 8 p.m. ET. The sitcom is the No. 1 comedy on television, and hundreds of fans attended the show's PaleyFest panel.
"Thanks to the all the incredible fans for showing up @paleycenter tonight," Galecki wrote on Instagram. "We all had a lot of laughs, didn't we? (Wish I coulda fit all your beautiful faces into the frame!) Be well and thank you dearly for all you love and support."
Hirsch is also known for playing John Lacey on Dear John and Alan Eppes on Numb3rs. The actor recently guest starred on The Goldbergs and will reprise Julius Levinson in Independence Day: Resurgence.