10. Paul Shaffer: George Costanza on Seinfeld

Paul Shaffer made a huge error in judgement when he said that he was “too busy” to consider the role of George Costanza that Jerry Seinfeld once handed to him on a silver platter.

The actor was not even required to audition for the part. One reason why the creators of “Seinfeld” were so fond of Shaffer for the role is because he looks so much like Larry David on whom the part is based.

He got a call from Seinfeld but never even called him back. Despite missing out on a role in the hugely successful sitcom, Shaffer has enjoyed a long career as David Letterman’s sidekick.

The 64 year-old musician has been the band leader on the popular show “Late Night With David Letterman” for almost 30 years and composed the opening theme song.

Shaffer did eventually decide to appear in a number of other TV shows such as “How I Met Your Mother”, “Law and Order: Criminal Intent” and even appeared as a square on popular 90s show “Hollywood Squares.” Although he has ventured into the world of acting on occasion, Shaffer considers himself a musician first and foremost.

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He has worked with an eclectic mix of talented artists over the years including Grand Funk Railroad, Diana Ross, Cher, Yoko Ono and Robert Plant.