An actor who starred on one of the most popular TV sitcoms is moving into a role on another wildly popular comedy series. ET Online reports that Judd Hirsch will play Leonard’s dad in an upcoming episode of “The Big Bang Theory.”

Hirsch starred on “Taxi,” which won 18 Emmys and was a force in the ratings during its five seasons in the late 1970s and early 1980s — the first four seasons on ABC and the final season on NBC.

“The Big Bang Theory” star Johnny Galecki said he played a role in bringing Hirsch to the show.

“I met this fellow a month or two ago and he’s a hero of mine and I knew that he was a hero of Chuck [Lorre] and Bill [Prady’s], so I just accosted him and cornered him and practically made him commit on the spot to play my father,” Galecki said, according to the report.

“Taxi” (Judd Hirsch, center)