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It’s a big night on “The Big Bang Theory.” Jerry O’Connell guest stars as Georgie, Sheldon’s older brother.

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Up until now, fans of Young Sheldon & Big Bang have only been able to imagine how Georgie tuned out. On tonight’s episode, Sheldon flies to Texas to invite his brother to his wedding.

“This is the first time George aka Georgie has been on Big Bang and it’s such an honor, it’s just so crazy,” said O’Connell.

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The trip becomes even more important for Sheldon after he learns that his mother won’t be attending his wedding unless he invites his brother.

“It’s rare in anything, forget about television, that there’s a young Sheldon, an old Sheldon, a young Georgie and a young Missy. It’s groundbreaking stuff we’re doing here.” said O’Connell.

O’Connell returns to CBS after playing Pete Kaczmarek on “The Defenders” back in 2010.

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Watch “The Big Bang Theory” tonight at 8pm EST on CBS.