Like some others highly-popular sitcoms, The Big Bang Theory had a ton of cameos and guest star appearances over the seasons.

Those included both real-life titans, such as Bill Gates and Stephen Hawking, and a huge number of actors, from renowned, to mostly remembered by nerds.

Some of those actors appeared in minor roles, while others played themselves. The latter included both Mark Hamill and Carrie Fisher.

And there was another actor owing most of his fame as Star Wars who appeared as himself in the series, and whose noteworthy performance – as well as mere fact of his presence on the set – left a deep impression on Jim Parsons.

That was James Earl Jones, the voice of Darth Vader. In one episode Sheldon met him eating at a restaurant and the two got along so well that they went on a string of adventures that evening, visiting a carnival together, singing a karaoke, and even pulling a prank on Carrie Fisher: they stopped at Fisher's house, rang her doorbell, and then ran off.

Fisher was not amused and immediately identified Jones as the likely culprit.

While the scenes were funny, filming them was a tense experience for Parsons, particularly at first. As he revealed in the interview, he have for The Big Bang Theory: The Definitive Inside Story of the Epic Hit Series book:

"I knew [James Earl Jones], obviously, as the voice of Darth Vader, and CNN. But more than that, I knew of him from his long legacy of the highest art of acting... …So there was something unsettling about the fact that he was there on our set in a weird way to me!"

But James was quick to dispel his apprehension:

"And he was so kind! And so game to play! But it was that weird feeling of, 'Are you sure you want to play with me? I don't know if this is the right fit for you. It's not because you're not doing it well; it's me! I blame myself!"

Of course, Parsons got even more nervous upon meeting Carrie Fisher on the set of the same episode, and the whole experience seemed just insane to him, through no fault of the guest stars.

As he noted: "I really should have seen a therapist over an episode like that."