Here it goes:
As you prepare, make a point of being conscious of your pacing and tone. Practice with an interview buddy or career coach. Allow your natural enthusiasm and personality to shine, but let's not frighten people. The interviewer(s) should be left with the sense that you really get the company, and you're excited to work there, but you're also composed.
Does that mean that the person has to show that he/she really likes the company he/she wants to work for?