On the night of The Big Bang Theory's series finale, spin-off Young Sheldon staged its biggest crossover yet in its Season 2 finale. Not only did we see young Sheldon, we saw young Leonard, young Penny, young Amy, young Howard, young Bernie, and young Raj.

The episode revolved around Sheldon's (Iain Armitage) excitement about the impending announcement of the Nobel Prize winner for physics (which, 30 years later, he would win). He planned a party and invited all his classmates to come listen to the announcement on the radio at 5 in the morning, with Swedish meatballs and everything. Meanwhile, Dr. John Sturgis (Wallace Shawn) had a breakdown until he came to terms with the fact that despite being a talented scientist, he would never win a Nobel Prize. "But Sheldon probably will," he said, hopefully.

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No one showed up to Sheldon's party, of course, not even Dr. Sturgis, and Sheldon listened to the announcement alone as he cried, feeling like he was destined to always be alone. But elsewhere at that very moment, Leonard was listening to the same report, Penny was sprawled out asleep, Howard was playing a video game while his mother yelled at him to go to bed, Raj was doing his homework on the other side of the world, Bernadette was asleep like a little angel, and Amy, his future wife, was reading Little House on the Prairie under the covers with a flashlight. "I was wrong," he said. Someday, he would find friends who loved him for exactly who he was.

It was an adorable tribute to the mothership show on the night of the series finale. Previous crossovers include the reveal that Sheldon and Amy had kids in the future, the origin of the "Soft Kitty" song, the origin of "bazinga," and a video message on TBBT from the past.

Young Sheldon will return for Season 3 in the fall. It's available to stream on CBS All Access.

Iain Armitage,<em> Young Sheldon</em>Iain Armitage, Young Sheldon

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