Ever since The Big Bang Theory spin-off prequel Young Sheldon premiered last year, the shows' producers have been open about their intentions to get the two shows to intersect. So far Young Sheldon has had numerous moments that showed the origins of iconic Big Bang bits like the "Soft Kitty" song, and Sheldon's friend Tam has appeared on both shows (played by Ryan Phuong on Young Sheldon and Robert Wu on TBBT.)

But with The Big Bang Theory ending this season, the writers had to come up with a full-on crossover before they lost the opportunity to do so. And they've finally figured it out: Young Sheldon's titular boy genius (Iain Armitage), his father George (Lance Barber) and his brother Georgie (Montana Jordan) will appear on a December episode of The Big Bang Theory, studio Warner Bros. announced Wednesday.

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No plot details are available at this time, but presumably they'll appear in a flashback or a memory or a dream sequence had by adult Sheldon (Jim Parsons), since time travel technology does not exist in the Big Bang Theory universe...yet.

The Big Bang Theory airs Thursdays at 8/7c on CBS, followed by Young Sheldon at 8:30/7:30c.

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Iain Armitage, <em>Young Sheldon</em>, Jim Parsons, <em>The Big Bang Theory</em>Iain Armitage, Young Sheldon, Jim Parsons, The Big Bang Theory