The Big Bang Theory time warp: Young Sheldon cast to appear in December episode

In a spacetime-bending surprise, Young Sheldon's Iain Armitage, Lance Barber and Montana Jordan are set to briefly guest star in an upcoming episode of the parent show, The Big Bang Theory.

CBS is tight-lipped about how the Young Sheldon characters Sheldon, George Sr. and George Jr. will feature in the modern-day world of The Big Bang Theory.

The Big Bang Theory recently explored what became of Sheldon and Tam's friendship with Robert Wu guest starring as adult Tam, while Jerry O'Connell was introduced as grown-up Georgie last season.

The Young Sheldon crossover episode is set to air in December. The Big Bang Theory is now in its twelfth and final season on CBS.