Bob Newhart is back as a ‘Star Wars’ ghost on ‘Big Bang Theory’

Bob Newhart is back on “The Big Bang Theory” as Sheldon’s (Jim Parsons) acidic childhood hero, Arthur Jeffries — aka science show host Professor Proton.

Jeffries/Proton passed away in Season 7, but has reappeared several times since as “Star Wars”-obsessed Sheldon’s Obi-Wan Kenobi spirit guide (complete with robes and light saber). In Thursday night’s episode (8 p.m./CBS), he appears in Sheldon’s dreams when there’s talk of rebooting Proton’s old TV show (Sheldon wants the job).

“I know I’m going to go in and it’s going to be good writing and it’s not a one-camera show, which I don’t know how to do,” Newhart, 88, says of the role, which earned him a 2013 Emmy. “I don’t know how you do those [one-camera] shows without an audience.”

Newhart is already a TV legend for “The Bob Newhart Show” and “Newhart,” which aired collectively for 14 seasons. “I’m not earning a living out there, but I enjoy doing it and I still have my fastball — or what’s probably now, according to Vin Scully, a changeup,” he says, alluding to Scully’s self-deprecating remark before Game 1 of the Dodgers-Astros World Series. “Let’s be honest. I’m 88. The lines don’t come that easily. But [Proton’s] opening line [in Thursday’s episode]: ‘What part of “Rest in peace” don’t you understand?’ The show’s writers are just so good at that.”

Newhart is asked if “The Big Bang Theory” is the only sitcom on which he will appear.

“I can’t imagine … well, I don’t want to say, ‘All the other shows stink and this is good,’” he says. “But at this point in my life, yeah, this is really the show I want to do.”

Note: “The Big Bang Theory” will be pre-empted on WCBS/Ch. 2 in New York by Jets football, and will air at 8 p.m. on WLNY. Check local listings.