Mark Hamill has paid tribute to 'The Big Bang Theory' after it ended after 12 series.

The 'Star Wars' actor congratulated the long-running sitcom for ''elevating nerd culture'' and admitted his brief appearance had brought him a new legion of fans after his cameo in season 11 saw him play himself as he officiated Sheldon's and Amy's wedding as a favour when Howard found his missing dog Bark.

He tweeted: '''Congratulations @bigbangtheory for 12 history-making years of laughter, elevating nerd-culture to unimagined new heights & triggering countless folks to ask me if I would please officiate at their weddings.

''Your fan, Bark Hamill.''

Another former guest star, astronaut Mike Massimino, also sent congratulations to the show.

He wrote: ''Congratulations to the entire cast & crew of

@bigbangtheory for 12 years and 12 great seasons. Thank you for all the laughs and for letting me be part of the fun for a couple episodes.(sic)''

The final episode featured a surprise guest appearance from Sarah Michelle Gellar and the 'Buffy the Vampire Slayer' actress was ''excited and honoured'' to be on the show.

She wrote on Instagram: ''It may not have been a date for me and Raj, but it was certainly an important date for @bigbangtheory_cbs and I was so excited and honored to be a part of it!!! Thank you for having me #bigbangtheory @kunalkarmanayyar (sic)''

Meanwhile, Rati Gupta, who joined the show for its final season as Raj Koothrappa (Kunal Nayyar)'s fiancee Anu, hailed her short run on the programme as the ''gift of a lifetime''.

She tweeted: ''Congratulations to everyone on the #BigBangTheory team for tonight's extraordinary accomplishment!!! It was the gift of a lifetime to join you for a season. What a season. What a SHOW. What an honor. (sic)''