The teaser for the crossover episode shows Sheldon (the adult version, played by Jim Parsons) feeling down in the dumps after the Nobel Prize-seeking theory he concocted with Amy was disproven.
In a bid to cheer him up, Amy digs out a video tape from Sheldon’s past that has a message from his younger self (played by Iain Armitage).
As the ten-year-old version of Sheldon perches on the edge of his bed, he says: “Hello Sheldon. If you’re watching this I assume something bad has happened. Something unfortunate and unforeseen. Something that’s making you question everything.”
“I’m so smart!,” older Sheldon grins. Classic.
Big Bang Theory airs on Thursdays on CBS in the US with the crossover episode expected to air in the UK on Thursday 18th December on E4