He is a dentist and Rita's boss in the dental office. He first appears in "A Novel Idea", where he is constantly asking Rita to help him with the patients.
He made a non-speaking cameo in "No Spoilers". He was seen at Rita's party and made appearances in a few scenes.
He was mentioned in "Net Gains", when he sponsored one of the basketball teams.
He was mentioned in “Pipe Dreams”, when Rita mentions his toothbrushes as a bathroom warming gift.
Dr. Feinstein is an old man with very little hair and a white mustache. He wears a light blue dentist gown over a white shirt. Inside of the gown's pocket, he has two pens, one is green, and the other is red.