'Big Bang Theory' at PaleyFest: 15 Things You Didn't Know

The Big Bang Theory at Paleyfest - Bialik and Parsons - H 2013
Kevin Parry for Paley Center for Media

The cast and creators behind CBS' The Big Bang Theory used their platform at PaleyFest on Wednesday night to offer a peek behind the curtain of the ratings behemoth, answering trivia about the geeky comedy and offering a window into what goes on behind the scenes.

Who came up with Sheldon's feel-good tune "Soft Kitty," the origins of Jim Parsons' alter-ego's catchphrase "bazinga!" and who had a major problem with the Smurf makeup? Plus how many takes did Kaley Cuoco and Johnny Galecki need to nail Penny and Leonard's historic "I love you"? Here are the 15 things you might not know about the series.

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1. It took only one take for Cuoco and Galecki to film Penny professing her love for Leonard. "Kaley said to Johnny, 'I don't know about you, but when we started the scene, the cameras and the live audience all went away and it was just us,' " new showrunner Steve Molaro recalled, noting that he told both actors the shot was beautiful and he knew they'd never get anything better.

2. The spot-on Mrs. Wolowitz voice -- which again was present, as it is every year at Comic-Con -- isn't the only impression Melissa Rauch does on the show. Turns out Bernadette's actual voice is based on her mother. "Only without the Jersey! Tonally, it's very similar," she said. 

3. Kunal Nayyar has his fingers crossed for Lucy (Kate Micucci) and Raj, but no matter what happens, he's glad to see his character evolve. "It's lovely to see him get to explore that side to himself, which has been amiss for so long," he said. "We can joke and laugh, but ultimately for him he really wants this. It's fun to see him vulnerable and to drop false sense of bravado. I don't know if he'll succeed, but it's really sweet."

4. When Sheldon punishes Amy (Mayim Bialik) with a spanking for faking illness in order to enjoy the ointment rub, it wasn't in the original script and was supposed to be off-screen. Parsons shared that there were three jokes -- a "hear no evil, see no evil, speak no evil" string of monkey scenes -- that ultimately were trimmed from the script one by one. "It was one of the hardest things we ever had to do because I found it tremendously amusing!" Parsons confessed, revealing that he had issues containing his laughter during production. "All week I was slapping that ass!" he joked. The bashful Bialik revealed that yep, her derriere was, indeed, red at the end of the taping. "There was some redness," she confessed. Added Parsons of his willing co-star, "You have no idea how game this one is for that!"

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5. Sheldon's trademark "Bazinga!" originated with writer Stephen Engel, who would set up playful practical jokes around the writers room, including putting together a grapefruit with tape. "I'd open it up and Stephen would say, 'Bazinga,' " executive producer Bill Prady recalled. "It was Stephen's word for 'gotcha.' " 

6. After featuring Leonard Nimoy and Stephen Hawking, the producers joked that their next dream guest star might be a bit too busy to make time for the CBS hit. "We've done some episodes about religion and science, and we thought Pope Francis might be good," Prady joked of Wednesday's newly elected pope. "He's probably too busy now." 

7. The cast really is musically inclined. Bialik learned how to play the harp after it was decided that it was Amy's instrument of choice; and Parsons learned how to play the theremin, so when scenes call for them to play, they actually are. As for their skill levels, Parsons joked his inability brought him to tears. For his part, Galecki also plays the piano. Chimed in Cuoco, "And when Penny drinks, she's really drinking!"

STORY: 'Big Bang Theory' Cast Surprises Showrunners With 'Call Me Maybe' Flash Mob

8. Cuoco's sister, Bri, choreographed the cast's surprise flash mob to "Call Me Maybe" -- and it earned her a job on two of co-creator Chuck Lorre's shows. Bri Cuoco played the woman who earns a marriage proposal in the background of Big Bang's recent Valentine's Day episode and choreographed a scene with 50 dancers on Two and a Half Men.

9. Origins of "Soft Kitty" revealed! After struggling to find the perfect song for neurotic Sheldon's healing ritual, it was Prady who came up with the ditty. "It's from my daughter's preschool in Sherman Oaks," he revealed. "It was from Australia, and one of the teachers heard it there."

10. After going as Smurfs for Halloween, Rauch shared the lengthy, painful -- and humiliating -- experience of having the blue makeup removed. Her regular makeup artist and two assistants were helping to remove the Smurf from her body using hot towels. "It was getting late and I'm starting to fall asleep … and I lifted my legs up to get the rest of the makeup off and heard the guy laugh and thought, 'Oh, they're just telling jokes' and I looked in the mirror and thought, 'What's that?! Dear lord Jesus, that's my business!' I had totally exposed myself! I put my legs down and just said to them, 'Long night!' " she said to laughs from the sold-out Saban Theatre in Beverly Hills. "That is the tale of my Smurfette."

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11. Lorre is the brains behind evil Wil Wheaton, but it was Star Trek fan Prady who had to make the call and break the news to the actor. "I didn't know this guy, and I had to call him and say, 'So you're playing yourself ... but you're a real dick!' " he said. "Will loved it."

12. That wasn't the only embarrassing conversation Prady had to have with a Star Trek alum. During a scene when Howard (Simon Helberg) has a dream about Katee Sackhoff, producers toyed with the idea of having George Takei do some voice work. "We wrote a line of Howard saying, 'I'm so confused,' and thought it'd be really funny if George Takei said, 'Confused? Perhaps I can help.' " Prady revealed. "How do I say to this guy that he's a possible homosexual fantasy? Finally I said, 'So you know you're gay, right?!' and he said, 'That's news I'll tell my husband!' "

13. Sheldon's Meemaw (his maternal grandmother) could show up. "We've talked about it, and I certainly wouldn't rule it out," Molaro said. "I don't know how she'd feel about Amy."

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14. What has Helberg learned from playing the lovable but style-challenged Howard? "I've learned the smallest pants size I can squeeze into!" he joked of Howard's colorful skinny jeans. As for his favorite belt buckle, it's anything that isn't sharp in the southern section that won't stab him when he sits down. "Sitting down is painful!" he joked.

15. When a nerdy fan in the audience asked the cast for dating advice, Cuoco spoke from Leonard and Penny's experience. "Keep knocking on your neighbor's door because eventually she's going to open it," she said to Parsons' immediate disapproval. "That's terrible advice!" he deadpanned.

The Big Bang Theory airs Thursdays at 8 p.m. on CBS.

Email: Lesley.Goldberg@thr.com; Twitter: @Snoodit