( CNN ) -- Fans of `` The Big Bang Theory '' gathered at Comic-Con for a panel about what happens inside the writers ' room of the the mega-popular CBS series , and they got more than they bargained for when some special guests made surprise appearances . Melissa Rauch , who plays Bernadette Rostenkowski , moderated the panel . Johnny Galecki , who plays Leonard Hofstadter , arrived in full `` Star Wars '' regalia , and the iconic physicist Stephen Hawking recorded a video message that featured him singing the show 's theme song . In the hour-long conversation , the actors , writers and producers teased details about the show 's upcoming seventh season , which premieres on September 26 . They confirmed Leonard will take the offer from Stephen Hawking that was presented in the sixth season 's finale . Kunal Nayyar 's character Raj Koothrappali will be figuring out how to speak to women without the influence of alcohol , and Bernadette and Amy ( Mayim Bialik ) may take their first trip away without Penny ( Kaley Cuoco ) . The real question , one that has been plaguing fans especially since last season , is whether Jim Parsons ' Sheldon Cooper and Amy will finally consummate their romantic relationship . `` I '' ll use Sheldon 's words and say 'It 's a possibility , ' '' writer Steve Holland said . `` I think part of the charm of their relationship is this glacial pace , '' creator/producer Bill Prady said . `` I think there 's such a sweetness to that . I think one of the virtues is how long it lasts . And it also means the show can last a lot longer . '' Take a video tour of Comic-Con . The writers also addressed whether the cast would ever find themselves at San Diego Comic-Con in an episode of `` The Big Bang Theory . '' `` From the first time we came here we said 'Oh my God we have to figure out a way to film an episode at San Diego Comic-Con , ' '' Prady said . `` But we do n't go into production until August so at the beginning of summer the cast goes off . Everybody 's in crazy places . And then the other problem is that we shoot on a stage , and we 're just not very good at filming out in the real world . So it remains a really good idea we have yet to find a solution to . '' Comic-Con is certainly the right place for this particular group of writers , however , who do a lot of research on the various science and geek topics that are integral to the show . `` We 're all pretty comfortable with the geekery , '' Holland said . `` Sometimes we have ideas from articles we 've read or we have a vague notion of , or sometimes we put in brackets 'Science to come . ' ''
'Big Bang ' Comic-Con panel teased upcoming season . The show will return for a third and final season, which is expected to air in 2015. Sheldon and Amy may consummate their relationship .