Although Leonard and Penny were ostensibly The Big Bang Theory’s lead couple, one particularly silly fight proved that the pair may have been even pettier than Amy and Sheldon.

By The Big Bang Theory’s finale, it was clear that the show’s priorities had shifted. When the series began, it was a hangout show that focused on Howard, Raj, Leonard, and Sheldon.

However, when the nerdy scientists gained a new neighbor in the form of Kaley Cuoco’s glamorous, free-spirited Penny, The Big Bang Theory’s focus shifted to Leonard’s attempt to woo her.

Leonard struggled with an obvious crush on Penny, and his initially unsuccessful romantic advances towards her were the driving force of seasons 1 and 2.

Soon, Penny and Leonard got together, and although they did weather numerous breakups and big fights, the pair had a relatively straightforward sitcom love story complete with marriage and children.

As this played out, Jim Parsons’ Sheldon overtook them as the show’s protagonist. Soon, it was no surprise when Young Sheldon was The Big Bang Theory’s first spinoff.