Warning: This article contains spoilers for the two-part series finale of The Big Bang Theory.

Nearly 20 million people in the US tuned in to watch the series finale of The Big Bang Theory - the best ratings the hit CBS show has had in over three years.

Finding a way to put an end to the show and its hugely successful 12-year run was never going to be easy.

And somehow the writers managed to jam-pack quite a lot into the two-part series finale which included the episodes 'The Change Constant' and 'The Stockholm Syndrome'.

This unaired scene from The Big Bang Theory's pilot could have changed the show entirely:

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I mean, Penny being pregnant with Leonard's baby was a perfect outcome for their on-again, off-again romance over the last 12 seasons.

But there was another detail - equally as special but a lot more subtle - that a lot of fans missed in the finale.

It's all to do with that time jump of 139 hours and 30 minutes which occurs while Leonard and Sheldon rebuild their atomic model.

Now, this time jump seems oddly specific - but there's a very special reason for it.

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Basically, if you work out how long it would take to watch every single episode of the show, you'll find it would take exactly 139 hours and 30 minutes. Clever right? And also a clear nod to viewers who have dedicated hours and hours of their time to the series, and are ultimately responsible for its phenomenal success.

The decision to end the show came in spite of the fact that the beloved sitcom was still attracting more than 12 million viewers each week, and that its cast, as a result, earned a fortune from each episode.

According to Business Insider, Jim Parsons, who played Dr. Sheldon Cooper, walked away with an eye-watering $50 million for the final two years of the show.

But considering the show's pilot episode aired all the way back in 2007, it was probably about time the iconic series came to an end.

'The Big Bang Theory' finale had an extra special meaning that everyone totally missed