"The Big Bang Theory" featured many recurring habits that defined Sheldon Cooper (Jim Parsons), but few were as consistent as his practice of knocking on doors three times — most often when visiting ...

The Big Bang Theory's success was largely due to the popularity of Jim Parsons' Sheldon Cooper, but the show took a toll on ...

Now that the character is regarded as one of his career-defining roles, it's hard to imagine anyone other than Jim Parsons playing Sheldon Cooper on "The Big Bang Theory." After all, the actor ...