The Big Bang Theory creators Bill Prady and Chuck Lorre have looked back on their hit show, revealing why one particular character didn't make the cut.

For the series' 15th anniversary, Prady and Lorre opened up on rewriting the character of Penny, whose final version was played by Kaley Cuoco.

Originally, Penny wasn't exactly kind to Leonard, Sheldon and the rest of the gang, and tried to take advantage of them. This meaner neighbour was named Katie and portrayed by actress Amanda Walsh.

the big bang theory kaley cuoco as penny
Sonja Flemming//CBS

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"In the first pilot, the female character (who, at that point, was named Katie) is kind of rough," Prady told Entertainment Weekly.

Katie was "dangerous in a way and [not] very nice to the guys". At the test screening, the audience "hated her", the creators explained.

"They hated her, but what was amazing was that they were defending Leonard and Sheldon so much," Prady added.

kaley cuoco and johnny galecki the big bang theory, with tea cups
CBS Photo Archive//Getty Images

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"Yeah, we didn't realize early on that the audience viewed them as children. They were very naïve and childlike, regardless of how intelligent they were. They were very vulnerable, and the audience didn't want a toxic presence around them," Lorre added.

After that test screening, Walsh wanted to come back in for the new version of Penny. However, the creators passed and recast the role as Walsh "had been so identified as that first character that it wasn't able to happen".

They then rewrote Katie to become Penny, cast Cuoco in the role... and the rest is history.

The Big Bang Theory aired on CBS in the US. You can buy the complete boxset now on DVD and Blu-ray.

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Stefania Sarrubba

Reporter, Digital Spy

Stefania is a freelance writer specialising in TV and movies. After graduating from City University, London, she covered LGBTQ+ news and pursued a career in entertainment journalism, with her work appearing in outlets including Little White Lies, The Skinny, Radio Times and Digital Spy

Her beats are horror films and period dramas, especially if fronted by queer women. She can argue why Scream is the best slasher in four languages (and a half).