Dr. Baldharar was a man who was heavily implied to be the owner of an animal fighting ring. He met Ross very briefly in "The One With The Fake Monica". He was portrayed by Harry Shearer. The character's name is only seen in the closing credits of the episode.
From his limited interaction with Ross, Baldharar seemed to be a horrible, compassionless, amoral individual who seemed to have little concern for the animals under his care so long as he could make some money from the smurfing.
When Marcel started humping everything, Ross started looking for a zoo to give him away to, and ended up meeting Baldharar for an interview in the coffee shop.
Though Ross had no idea that Baldharar's "zoo" was an animal fighting ring, Baldharar seemed to have pretended to represent a zoo's interest in Marcel. This is seen in his asking Ross strange questions such as if Marcel would fight other animals if cornered and if he was capable of handling a hammer or small blade; and then avoiding Ross' concerned follow up questions.
Joey and Chandler burst into the shop with Marcel in order to tell Ross that the monkey had been accepted at San Diego Zoo. Baldharar in a last ditch effort to win over Marcel; then promised Ross that he would "start (Marcel) off against a blind rabbit and give (Ross) twenty percent of the gate."
The scene ends with Ross, Joey and Chandler backing away from Baldharar in horror at his apparently compassionless personality and after realizing his true intentions. Baldharar was never seen again after that.