These Before And After Pics Of "The Big Bang Theory" Cast Show Just How Much Has Changed On The Series

12 years later...

After 12 long years, The Big Bang Theory is coming to an end, making it the longest-running multi-camera sitcom in TV history.

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In honor of the series finale, here's a look back at the cast:

Kaley Cuoco as Penny

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Season 1, Episode 1, "Pilot" vs. Season 12, Episode 23, "The Change Constant."

Jim Parsons as Sheldon Cooper

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Season 1, Episode 2, "The Big Bran Hypothesis" vs. Season 12, Episode 23, "The Change Constant."

Johnny Galecki as Leonard Hofstadter

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Season 1, Episode 2, "The Big Bran Hypothesis" vs. Season 12, Episode 22, "The Maternal Conclusion."

Kunal Nayyar as Rajesh Koothrappali

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Season 1, Episode 3, "The Fuzzy Boots Corollary" vs. Season 12, Episode 17, "The Conference Valuation."

Simon Helberg as Howard Wolowitz

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Season 1, Episode 1, "Pilot" vs. Season 12, Episode 22, "The Maternal Conclusion."

Melissa Rauch as Bernadette Rostenkowski-Wolowitz

Michael Yarish / WARNER BROS.

Season 3, Episode 10, "The Gorilla Experiment" vs. Season 12, Episode 22, "The Maternal Conclusion."

Mayim Bialik as Amy Farrah Fowler

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Season 4, Episode 5, "The Desperation Emanation" vs. Season 12, Episode 22, "The Maternal Conclusion."

The end of an era!!

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