The Big Bang Theory casts Sheldon's brother

The 44-year-old actor tweeted that he was "Beyond Bazinga'd" to be joining the cast as George Cooper in the upcoming 11th season of the hit US sitcom.

He also joked that Montana Jordan needed to help him with lines. Montana is the teenage actor starring as George in Young Sheldon - the Big Bang prequel about Sheldon's younger years.

O'Connell is best-known for starring in Jerry Maguire and Sliders, while Deadline reports producer Steve Holland as saying of the casting: "This is the first time it is being announced, so don’t tell anyone."

It was also revealed that the finale to season 11 would focus on Sheldon and Amy's wedding.

Jim Parsons, Johnny Galecki, Kaley Cuoco, and Kunal Nayyar were also on the panel alongside producers Holland and Chuck Lorre, Steven Molaro and Bill Prady.

Parsons and Nayyar paid tribute to Stephen Hawking, who passed away in March and made a cameo appearance on the show in 2012.

Of filming with Hawking, Parsons said: "It was frightening! He is the smartest person you are ever going to meet. It was a true honour. I always left the room fast before I said something stupid."

Meanwhile Nayyar added: "I mourned his death like Kunal and like Raj — his presence was a character on our show."

The panel also reportedly spoke about Bill Gates making a cameo appearance on the show, which had previously been reported.