Well first off, getting an interview means that you've bypassed the initial mass rejection so the school has taken notice of you in some way, shape or form. I would have to say that they will keep in mind of your GPA and PCAT scores and see if you are who you say you are.
I wouldn't be surprised if a high GPA/PCAT candidate has more leeway on how well they do on an interview as opposed to a low GPA/PCAT candidate. That's not to say that an exceptionally strong candidate can bomb the interview and still be accepted.
If an interviewer's first impression is "herpaderp derp" with their eyes crossed while ripping a huge fart that makes Mother Nature turn her nose up, no amount of application awesomeness can save you.