'The Big Bang Theory'
CBS' "The Big Bang Theory" commands more than $325,000 for a 30-second ad spot. CBS

“The Big Bang Theory” is about to get bigger as the cast adds television legend Bob Newhart for a guest star role on the hit CBS sitcom this May.

TV Line first reported the news on Thursday, stating that the star of “The Bob Newhart Show” and “Newhart” will play “Professor Proton,” the former host of an educational science show akin to “Bill Nye the Science Guy.”

NBC confirmed the news later in the day, adding the producers Bill Prady and Steven Molaro had already hinted at an appearance by Newhart at “The Big Bang Theory’s” PaleyFest.

"We have a really great actor coming up," Prady, told the audience, adding that Newhart would be different than most “Big Bang Theory” guests because "he's not from the world of science or science fiction."

"The part he's going to play is someone [Sheldon and Leonard] loved when they were kids," Molaro said. "We're really excited about it."

Viewers learn in the episode that Professor Proton was a huge hero to both Leonard and Sheldon, though Sheldon may take things a little too far as he books Newhart’s character for a private appearance at their home. The episode is slated to air on May 2.

Newhart, 83, became one of the most well-known comedians on television with his 1970s sitcom “The Bob Newhart Show.” Four years after its cancellation, he returned to the small screen in 1982 with “Newhart.” Famously, in the last episode of “Newhart,” the entire sitcom was revealed to be a dream of his “Bob Newhart Show” character Robert Hartley, as Newhart woke up in bed describing the entire show as a crazy dream.

Newhart couldn’t be coming into “The Big Bang Theory” at a more popular time. According to the Hollywood Reporter, “The Big Bang Theory’s” first episode of 2013, “The Egg Salad Equivalency,” brought in a whopping 19.25 million viewers on Thursday night, breaking records for the show.

Even more impressive was the show’s record-breaking Nielsen rating of 6.1 in the 18-49-year-old demographic, meaning that not only is the show extremely popular, it’s extremely popular with the most popular audience for advertisers.