Since the main characters of Sheldon Cooper, Leonard Hofstadter (Johnny Galecki), Howard Wolowitz, and Rajesh Koothrappali (Kunal Nayyar) work at the California Institute of Technology, they aren’t just into science fiction; they also love science fact and the champions of science. Famous faces within the scientific community, such as Neil deGrasse Tyson, Bill Nye, and Stephen Hawking, popped in once in a while. Actually, Hawking popped in more than once.
Hawking appeared in multiple episodes throughout the series’ run, including “The Hawking Excitation,” “The Extract Obliteration,” and “The Celebration Experimentation.” He became fast friends with Sheldon. Moreover, he told Sheldon to turn the finger of Amy Farrah Fowler (Mayim Bialik) into Saturn and “put a ring on it.” Hawking was once considered the smartest man on the planet, so you couldn’t ask for better advice.
On March 14, 2018, Hawking died peacefully in his sleep (via the BBC) at the age of 76. According to the article, he was diagnosed with a rare motor neuron disease at the age of 22, and doctors predicted he only had a few years to live. Hawking defied the odds, but he lived most of his life in a wheelchair and used a voice synthesizer. Who can say how many more “The Big Bang Theory” episodes would have guest-starred Hawking had he not passed away? Given his fictional incarnation’s relationship with Sheldon, Hawking might have shown up for the series finale.