Actor Jim Parsons opened up about his time spent on the hit show "The Big Bang Theory," joking that he knows "where all the bodies are buried."

During Wednesday evening's appearance on "The Tonight Show," Parsons told host Jimmy Fallon that he’d participated in 20 hours of interviews with author Jessica Radloff for her book "The Big Bang Theory: The Definitive, Inside Story."

"Honestly, it was really the only way I thought it was worth doing, because I thought… if they’re just going to talk for an hour or two, it’s like, [what’s the point?]," he told Fallon. "So I was like, ‘Cool, let’s do it.’ And it was really interesting, because it was sort of a decompression of those 12 years that I didn’t realize how helpful that would be."

The actor, who played Sheldon Cooper for 12 seasons, continued. "Other people would jog memories when she’d come back to you with other questions. They’re like, ‘They said . . . ’, I’m like, ‘That’s right, that happened’ or whatever. I had my own little box of what that time was in its own way. I know where all the bodies are buried, I like to say."

'BIG BANG THEORY' STAR JIM PARSONS REVEALS MOMENT OF 'CLARITY' THAT LED TO HIS EXIT FROM SHOW

Earlier this month, Parsons opened up about his character Sheldon's romantic interest-turned-wife Amy, played by Mayim Bialik. The actor said he was not willing to imagine a scenario where Bialik's character would be written off the program.

Mayim Bialik as Amy Farrah Fowler and Jim Parsons as Sheldon Cooper in 'The Big Bang Theory'

Mayim Bialik was introduced in season three to the "Big Bang Theory" fan base as Amy Farrah Fowler, a romantic interest for Jim Parsons' Sheldon Cooper. (Bill Inoshita/CBS)

Originally appearing in one episode, Bialik's character Amy Farrah Fowler was introduced as a romantic interest for Sheldon. "There was some negative attention when I joined the cast, because some people held Sheldon very near and dear to them and didn't want him to change or become a cheesy boyfriend," Bialik shared in the new book.

Parsons recalled thinking of Bialik's addition to the show in the season three finale, "'I will not let this character go without a fight.' That was notable for me, only in that I almost never disagreed with the writers. At some point, I felt a certain way about working with Mayim that I was like, if for whatever reason we seemed to be weaning her off of this show as a character, I would go and talk to them."

Jim parsons Mayim Bialik

In season 11, Sheldon Cooper (Jim Parsons) marries Amy Farrah Fowler (Mayim Bialik). (Michael Yarish/CBS )

Alas, Bialik was brought back the following season.

Big Bang Theory

This photo provided by CBS shows Melissa Rauch, from left, Simon Helberg, Johnny Galecki, Kaley Cuoco, Jim Parsons, Mayim Bialik and Kunal Nayyar in a scene from the series finale of "The Big Bang Theory." (Michael Yarish/CBS via AP)

"After my episode in the season three finale, I literally thought my character might never come back. I had been out of the industry for so long … it really could have gone either way," she remembered.

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"The week that I was offered a regular contract, I had told my manager, 'I think this is my last episode; I think they're done with me and have done all they want to do with my character.' And that made me really sad. I told my manager, and she called me back later that day and said, 'You're not going to believe what call I just got. They'd like to offer you a full position as a regular!'"

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The popular show would go on to span 12 seasons, becoming the longest-running multi-camera comedy ever with 279 episodes.