The Big Bang Theory has become such a smash hit since its debut in 2007 that it's attracted its fair share of celebrity cameos, from Bill Nye (the Science Guy) to Stephen Hawking himself.
But the show's co-creator Bill Prady has revealed that one person was so keen to make an appearance that they launched their own campaign to be cast.
Speaking to Digital Spy at PaleyFest, he revealed that Neil DeGrasse Tyson approached the production team with a request to appear on the sitcom.
"We've had the experience a couple of times of people forwarding fan mail that was sent to them, suggesting that they would be a good fit on The Big Bang Theory and saying, 'Well, look, it's not coming from me!'" Prady said.
"I will absolutely not embarrass the head of the Hayden Planetarium in New York City by saying who that might've been."
Of course, astrophysicist Tyson has been the director of that particular planetarium since 1996, so there's no doubt as to who Prady meant.
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Tyson made a cameo in a fourth season episode, 'The Apology Insufficiency', in 2010 and was memorably told to "shut up" by Sheldon Cooper (Jim Parsons), who was angry at Tyson's role in Pluto being disqualified as a planet.
Prady also teased another upcoming cameo, revealing that "a prominent science-fiction and comic book writer is being discussed for an upcoming episode – a very geeky cameo!"
That mystery cameo may have to take place fairly soon, as it's quite possible that the next season – the show's 12th – will be its last.
That's according to actor Johnny Galecki (Dr Leonard Hofstadter) at least, as he recently suggested that the cast would be happy to wrap things up at that point.
"The only manner in which the cast has discussed wrapping [the show] has been that we're all going to be very sad when that day comes," he said.
"But I think at this point everyone's very comfortable with 12 seasons being a good time to go home and see our families."
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Reporter & Sub-Editor, Digital Spy Susannah is a freelance writer and sub-editor, specialising in the entertainment industry. She graduated in 2014, with a BA in English and American Literature and Creative Writing, and an MA in Creative Producing. She’s been writing for Digital Spy ever since, after first getting involved through work experience, and has written hundreds of stories for the site on a range of topics, from The Sims to Doctor Who. Susannah has also written for Reveal Magazine. Her special interests are soaps (her Mastermind subject would be 2000s Coronation Street), Marvel and Star Wars. She can also quote far too many lines from Friends and Brooklyn Nine-Nine.
