I think you may be referring to a 'vive' or 'viva' voce (sp?) examination. Basically, it's an aural exam in the form of a sort of interview, usually so that the candidate can elucidate on his or her written paper or thesis.
Sometimes such exams are standard procedure - I believe they're commonplace in medical exams and at masters and doctoral level. They can also be used to clarify any dubious papers when plagiarism is suspected.