Jasper, a 2-year-old pit bull, can't run, jump and play with other dogs in New York's Central Park because he is not well socialized and has no patience.
His owner, Eric McLendon, says he is a gentle and loving dog, but he can appear very aggressive when he first meets someone.
Jasper is about to meet his match in the dog whisperer, Cesar Millan.
"He needs rehabilitation. He needs training," Millan said.
The instant McLendon hands over the leash, the dog relaxes. It's been said the dog whisperer can talk to dogs in their language.
"I'm Cesar Millan. I rehabilitate dogs, but I train people," he said.
He has channeled his talent into a hit show.
Every week on the National Geographic channel, Millan, 36, takes on a new problem dog and dispenses tough love to the dog and its owner.
The most serious cases call for a stint with the pack at Millan's "dog psychology center" in South Central Los Angeles.
The transformations are often miraculous, which may explain why Millan's fans are so rabid and so numerous.
A recent seminar he gave in Columbus, Ohio, drew 1,700 people -- a third of the audience didn't even have dogs.
Millan has no formal training, but that doesn't seem to matter to his celebrity clients like Oprah Winfrey, who asked him for help with her dog, Sophie.
Millan has come a long way from his farm upbringing in Mexico where he learned how to handle dogs from his father and grandfather.
"That's pretty much what I felt that was my call," he said, "and I didn't fight about it."
Millan can be remarkably doglike.
"When I'm with a dog, I want to be one," he said. "Two species but moving as one."
He used this ability to relate to canines to help Jasper.
Millan says like most owners, McLendon had made the mistake of putting affection before discipline, and most importantly, before exercise.
"We all know how to give affection. I mean, I'm not going to teach America about giving affection to a dog. You know they throw birthday parties for dogs," he said. "But they don't know how to lead a dog properly. They don't know how to set rules, boundaries, limitations. It's easier now to ask him to relax."
Millan used his physical techniques on Jasper.
"So our conversation is more energy, body language than verbal," Millan said. "So you went through an explosion, and then now you are riding the wave."
Millan's techniques, which consist of yanking and poking, don't go over well with everyone. Some animal advocates say he is abusing the dogs.
"Well, yeah, in a lot of people's mind that is abuse, but what I am creating is a calm, submissive state," Millan said. "It is a physical touch. They are supposed to snap the brain out of it."
Millan's fan base skews strongly female.
"He's so great," one of Millan's female fans said at a book signing. "He's so fine. He's so fine."
"I love this man," another said. "I just kissed him and hugged him. I think he's so great with these animals, and I wanted to see him. I took off early from work -- don't tell nobody -- to get here."
Yet he wasn't always so great with women. His wife nearly left him early in their marriage. He said he tended to bring his philosophy about showing affection last into their relationship.
"She totally embraced that American woman thing. They don't put up with anything," he said. "She just moved."